Voldemort hid one of his Horcruxes inside Hogwarts. It seemed to be relying on security through obscurity as far as protecting it. But as we know, it ended up not being so secure because it wasn't so obscure - Harry Potter knew about the Room of Hidden Things.

My question is, the way Rowling describes this hints at the fact that Riddle had an assumption that very few people would ever stumble upon that room. WHY???

First, let's show Harry's theory on what Voldemort was thinking, how and why:

Here's Harry understanding Voldemort's thinking in HP7 once he figured out where the Diadem was (bold emphasis mine):

Tom Riddle, who confided in no one and operated alone, might have been arrogant enough to assume that he, and only he, had penetrated the deepest mysteries of Hogwarts Castle. Of course, Dumbledore and Flitwick, those model pupils, had never set foot in that particular place, but he, Harry, had strayed off the beaten track in his time at school – here at least was a secret area he and Voldemort knew, that Dumbledore had never discovered –

...and later on, with Harry explains the location to Ron/Hermione:

“He hid it exactly where I had my old Potions book, where everyone’s been hiding stuff for centuries. He thought he was the only one to find it. Come on.”

“And he never realized anyone could get in?” said Ron, his voice echoing in the silence. “He thought he was the only one,” said Harry.


Yet, from available evidence, that seems to be a completely wrong assumption, even at Voldemort's time.

Let's examine that last quote again, with emphasis on other info available:

“He hid it exactly where I had my old Potions book, where everyone’s been hiding stuff for centuries.” ...


“And he never realized anyone could get in?” said Ron, his voice echoing in the silence. “He thought he was the only one,” said Harry. “Too bad for him I’ve had to hide stuff in my time... this way,” he added. “I think it’s down here... “

They sped off up adjacent aisles; Harry could hear the others’ footsteps echoing through the towering piles of junk, of bottles, hats, crates, chairs, books, weapons, broomsticks, bats...


OK, so if there's a truckload (or train-load, by the description) of stuff in that room, isn't the only reasonable conclusion: "the room is a fairly popular destination with plenty of people who've found their way there in the past, and therefore, likely, plenty who will in the future"?

Doesn't matter what your arrogance level is, the evidence seems to point to only one conclusion - it's quite fine as a place to temporarily bury your dirt so teachers won't tag you for your misdeeds, but this is NOT the place to hide something that you want permanently safe!

So why did Voldemort make such a moronic mistake?

  • 25
    Another questions would be: Why did Harry assume that Voldemorte thought no one else knew about the room?
    – Xantec
    Commented Jan 9, 2012 at 0:57
  • 10
    @DVK or Voldemorte hid the horcrux there knowing that often times the best lace to hide something is in plain sight. or in this case hidden among train-load of otehr hidden items.
    – Xantec
    Commented Jan 9, 2012 at 1:17
  • 4
    @OghmaOsiris The feature/phenomenon is the "Room of Requirement." The particular form it takes as the room where things (including the book, cabinet, diadem, etc.) are hidden is called the "Room of Hidden Things."
    – Kevin
    Commented Jan 9, 2012 at 1:25
  • 12
    If Voldemort didn't have such disdain for Muggles, he could have sent a Horcrux to the Moon with an Apollo mission and no wizard would have been able to destroy it.
    – Nick
    Commented Aug 2, 2012 at 15:22
  • 7
    Either Dumbledore made up his story about the chamberpots, or Rowling has a plot hole, since to enter the RoR you have to walk past it 3 times thinking about what you need. No one needing to pee in the middle of the night walks up and down a blank hallway far from their bedroom; they hurry to the nearest toilet which would have been in their own suite anyway.
    – user41482
    Commented Feb 4, 2015 at 22:03

14 Answers 14


It's the room of requirement. Voldemort required a room to hide his item in. Where better to hide a small, reasonably nondescript item than in a pile of junk? If not then it's possible when he hid it it wasn't full of junk; Harry required a room full of all of the small, nondescript items that may have been the diadem. Yes he knew what it was but maybe not specifically enough to single it out.

The room also has a habit of overdoing things, like when Dumbledore needs the loo and finds tens of chamberpots there, when one would do:

"Only this morning, for instance, I took a wrong turning on the way to the bathroom and found myself in a beautifully proportioned room I have never seen before, containing a really rather magnificent collection of chamber pots. When I went back to investigate more closely, I discovered that the room had vanished. But I must keep an eye out for it. Possibly it is only accessible at five-thirty in the morning. Or it may only appear at the quarter moon - or when the seeker has an exceptionally full bladder."

~Christmas Ball, Goblet of Fire,

  • 3
    @TangoOversway Yes. Very early on, if I recall. He is musing on the secrets Hogwarts still holds, even from him. Harry at the time believe he may be joking.
    – Jeff
    Commented Jan 9, 2012 at 5:49
  • 3
    @TangoOversway:Yes, in Goble of Fire at the Christmas Ball.
    – apoorv020
    Commented Jan 9, 2012 at 6:15
  • 1
    @TangoOversway I've a feeling it's in PS after Harry finds the Mirror of Erised, thought I haven't got any of the books to hand.
    – AncientSwordRage
    Commented Jan 9, 2012 at 10:01
  • 4
    Based on Dumbledore's experience, then, it sounds like what Riddle required of the Room was that it validate his sense of being exceptional. So, why should it be a room of drab schoolkids' junk? For him, it would be a shrine to his own cleverness.
    – Ryan Reich
    Commented Jun 14, 2014 at 16:55
  • 8
    +1 "The room also has a habit of overdoing things": It would explain why the room was full of junk and we could assume most of it didn't belonged to students but were produced by the room. Thus, it would have been a possibility that nobody would have ever been there before Voldemort hid its Horcrux. (Or at least Voldemort would have been able to assume it.)
    – Ananas
    Commented Jan 3, 2015 at 19:10

It is a pebble-on-the-beach approach - how many people are going to find the room, know that there is a diadem in there that is significant (and know what a diadem is, for that matter), be able to find it, and then, destroy it? Voldemort was relying on the answer being no-one, at least until such a time as he was powerful enough to not be bothered.

And remember that finding the Room of Requirement is not the same as finding the Room of Hidden Things. Finding the RoR is one challenge, but finding it as the RoHT - reliably, so that you can come back to it - was a one in a million chance.

And @OghmaOsiris - the fact that three schoolchildren thwarted Voldemort several times is one of the suspensions of disbelief required for the series.

  • I know, i was just making a funny point, lol Commented Jan 9, 2012 at 10:20
  • Yes, but it is a valid point, actually. The story required them to achieve things that were - even within their world - extremely improbably, if not impossible. Commented Jan 9, 2012 at 10:48
  • @OghmaOsiris Does it require disbelief though (and I know it's in the answer but this way both see it)? They often had help and Hermione was very much part of that help. Harry wouldn't have survived without Hermione and that's for certain. Harry and Ron would have been killed. There of course are other chances: the wand core, the phoenix and so on but Hermione was critical to their survival. Still it's easy to see how Voldemort would believe that Hogwarts was the safest place when he had full control of it - and his Death Eaters were on guard (etc.).
    – Pryftan
    Commented Jul 7, 2018 at 0:03

I think Voldemort's arrogance has to be included in the equation. Voldemort truly believed that he was the only person to discover the Room of Hidden Things/RoR/CaGR, whether that seems logical or not. After escaping Gringotts and jumping off the dragon into the lake, Harry finds himself inside Voldemort's head, able to read Voldemort's thoughts about the Horcruxes:

[Voldemort] As for the school: he alone knew where in Hogwarts he had stowed the Horcrux, because he alone had plumbed the deepest secrets of that place ...

And Hogwarts ... but he knew that his Horcrux there was safe, it would be impossible for Potter to enter Hogsmeade without detection, let alone the school. Nevertheless, it would be prudent to alert Snape to the fact that the boy might try to re-enter the castle ...

Deathly Hallows - Page 444 - British Hardcover

Harry says, "He thinks the Hogwarts one is safest, because Snape’s there, because it’ll be so hard not to be seen getting in, I think he’ll check that one last, but he could still be there within hours –'

I also think Voldemort was emotionally compelled to hide at least one Horcrux in Hogwarts. Hogwarts -- not unlike for Harry -- was the only place Tom Riddle/Voldemort ever considered a home. Given his propensity for attachment to things (Hogwarts, Founders' items, the snake Nagini) rather than people, it makes sense that 1) he would want to hide a Horcrux in the place that he considered home and 2) due to his emotional attachment to Hogwarts, he could have very well thought that the castle itself claimed him as its ultimate master. If so, then of course no one else would have discovered the Room of Hidden Things, because Hogwarts belonged to Voldemort (in his mind) and Voldemort alone. This represents a twisted sense of entitlement, the inability to see others as equals (seeing people as unskilled in achieving the high level of magical power that he himself had), and unable to imagine that any wizard other than himself could possibly discover or work out the secrets contained within the castle. So, to answer the question, the reason Voldemort made such a moronic mistake in leaving the diadem Horcrux essentially in plain view is because his thinking is distorted and skewed -- for he recognises no other as an intellectual equal or someone to learn from (he already believes he knows it all -- and is full of logic and thinking errors.) Once again, Voldemort underestimates that which he does not value, and there is so much that he does not value that his perception of the world is myopic, imbalanced, and not reflective of reality.

  • 1
    "I also think Voldemort was emotionally compelled to hide at least one Horcrux in Hogwarts. Hogwarts was the only place Tom Riddle/Voldemort ever considered a home" - dumbeldore says exactly that in the books Commented Dec 1, 2013 at 3:02
  • What you say is true but that the trio could actually get into Hogwarts when the Death Eaters were in control is remarkable; he was wrong but it wasn't a bad assumption.
    – Pryftan
    Commented Jul 7, 2018 at 0:05

Voldemort knew other people knew about the room, he must have, considering it is written in the book the history of Hogwarts, which Hermione points out. He knew this, and so used the room to hide the horcrux. Like someone said earlier, how many people are going to accidentally find the room of requirement, accidentally find the diadem and accidentally destroy it? Not many, I'm guessing.

Also, as Cho points out, the diadem has been lost for centuries, and no living person has seen it (which isn't technically correct, as Voldemort had seen it, but anyway...). This means that even if someone saw it, they wouldn't think it was the lost diadem.

The 'truck load' of stuff in the room may not have necessarily been hidden by students. Someone needs a place to hide their stuff, you are hardly going to be shown a plain room, with nothing to hide the object in. All the other items have probably been created by the room to help the student hide the item.

  • 1
    "how many people are going to accidentally find the room of requirement" - 0, u cant find it by accident. Commented Dec 1, 2013 at 2:59
  • 1
    @tryingtogetprogrammingstraight Didn't Dumbledore find it by accident looking for a bathroom?
    – BrandonL
    Commented Apr 7, 2017 at 15:22
  • @BrandonL That's correct.
    – Pryftan
    Commented Apr 16, 2018 at 23:10
  • Also, George and Fred found it by accident when they needed a play to hide from Filch.
    – Davin
    Commented Dec 29, 2020 at 18:47

why did Voldemort make such a moronic mistake?

It probably would have been a moronic mistake not to hide one of his horcruxes there.

He needed to hide many horcruxes, and they needed to be unique hiding places. Hogwarts is one of the safest places in the Wizarding World. Access to the Room of Requirement is not well known. The ability to repeatedly access the Room of Hidden Things is even less likely. If you happen to get past all of that, you still have to almost literally find a needle in a haystack, and that is assuming you know what the horcrux actually is and looks like.

Voldemort kept his ownership of many horcruxes a secret, and certainly it would have been unlikely that someone could discover that one of them was Ravenclaw's diadem, given that Voldemort made the horcrux and hid it so quickly, and that the Ravenclaw ghost—the only person who had conclusive information about the diadem—was so closed off.

  • Well more like he believed he kept his Horcruxes (and the number too) secret... But yes to the rest of your points.
    – Pryftan
    Commented Apr 16, 2018 at 23:15

The simple explanation is that people can stumble into the room (like Dumbledore did), without knowing what it was and how to get back in. So, Voldemort may have thought that yes, people can come in here, but only accidentally, I am the only one who can come in here at will. If Dobby had actually not told Harry about this, no other human in the universe would have known about the room, and it would have been safe.

Furthermore, even if somebody goes into the room, the chance that they will recognize the diadem as something significant is pretty negligible. (Or even if they know about it, finding it in a room full of junk is going to be pretty difficult.)

You can call this kind of thing, security by obscurity. Voldemort seems to be following the same principle as the dungeon in the first book, use as many different kinds of security as possible, so that even a strong wizard like Dumbledore can't find and destroy each one.

  • Yet three 11year olds stopped them pretty easy lol Commented Jan 9, 2012 at 7:14
  • Security through obscurity, however, isn't security on its own..and that's sort of what this is. In this case it's a single layer isn't it? Unless you mean all the different ways of hiding the Horcruxes; but then again each Horcrux is a fraction of his soul as a whole. I'm curious what you believe is different. Of course it's probable he believed that since nobody alive had seen it he needn't worry about it being unsafe because nobody would know about it in the first place. Then again he felt that about his Horcruxes too.
    – Pryftan
    Commented Apr 16, 2018 at 23:14

Don't forget that pride is Voldemort's fatal flaw. He has a very inflated opinion of himself and cannot conceive of anyone being smarter (or even just as smart) than himself. Even in spite of the evidence (he found the room and there is proof others used it before him) Voldemort does not want to believe that others might have his knowledge and capabilities.


Think of how many lucky breaks and flashes of inspiration Harry and co had to find that horcrux. First

  • To even know that there were Horcruxes and what they did (it was not exactly common knowledge)
  • To workout what Voldemort's plan was
  • To have the nerve to actually try to stop him
  • For Dumbledore to stumble onto the room
  • For Dumbledore to mention it to Harry
  • For Harry to believe him and later try to use the room
  • For Harry to actually be able to use the room
  • For Dumbledore and Harry to work out that Voldemort had hidden a horcux under their noses at Hogwarts
  • For Harry to workout what the Horcrux was
  • For Harry to workout where the Horcrux was
  • For Harry to find it and have a means for breaking it

If any of these had not gone their way the horcrux would still have been safe. The hiding place was very secure, no one could anticipate all of the above but even if it is found then that does not really matter as there are six more anyway.

  • While your point still stands, D did not just casually "mention" the room to Harry. Throughout the books D says things to Harry that Harry takes as idle and casual conversation but that we later learn were specific clues D was feeding him. Your list is not entirely chance here. Commented Dec 8, 2012 at 5:28
  • Was there any evidence that D knew there was a horcrux in there? If not then it was chance that he mentioned the room to Harry and there happened to be a horcrux in there that the could never have found otherwise.
    – Stefan
    Commented Dec 8, 2012 at 9:25
  • Quite a lucky break that it happened to be exactly where that horcrux was then
    – Stefan
    Commented Dec 8, 2012 at 23:56
  • I'm not arguing there wasn't luck involved, just making the point that not all of what you list was all "luck." In fact, at the end of "The Sorcerer's Stone" While in the hospital wing, Harry says to H and R, "He's a funny man, Dumbledore. I think he wanted to give me a chance. I think he knows more or less everything that goes on here, you know. I reckon he had a pretty good idea we were going to try and instead of stopping us, he just taught us enough to help. I don't think it was an accident he let me find out. . . " Rowling is indicating D has a plan and knows more than he lets on. Commented Dec 15, 2012 at 0:55
  • I would guess D did at least have guesses about what the horcruxes were and where they would be found. You mention the kids being lucky the had the means to destroy the horcruxes, but Dumbledore specifically left that sword to them in his will and they went to great lengths to obtain when the ministry did not just hand it over (with a little help from another professor of course). D clearly has more than a "common knowledge" and got injured himself in learning the details of V's plan. Commented Dec 15, 2012 at 0:58

Voldemort probably thought he was very clever, stumbling upon the Room of Requirement. The boatloads of stuff looked like they hadn't been touched for years, and he probably figured the chances of anyone using the same section (form?) of the Room of Requirement, let alone knowing where to find the diadem, let alone knowing that it was even a Horcrux, was very, very low. Which it was, but it was on that very slim chance that Harry got it.

  • All true. But I'd add he was very clever... The fact he believed himself superior being wrong is another matter entirely although it's presumably why he believed he was the only one to discover all of Hogwart's secrets.
    – Pryftan
    Commented Apr 16, 2018 at 23:25

I think that possibly a lot of people who found the room over the years probably believed they were the only ones to do so - at least the only ones of their generation. The only reason it was so well known amongst the students in Harry's time at school was because it was used for Dumbledore's Army meetings and then later as a hideaway by Neville and his little band of rebels in DH. Even then, the room changed its function as neeed. It could be that many people who found the room, found it in a different configuration to that Voldemort and Harry had found it in to hide their items.


I think that you are looking at the room the wrong way. I think voldemort believed he alone knew how it operated, and that the room was what it was.

Obviously people had been hiding stuff there forever, but I think Riddle used the room in the same way Neville does in the sentence book. On a consistent basis, knowing the rules.

Remember that before Harry, the only one who knew how to get it consistently were the house elves, which Riddle believe are beneath him.

He believes others stash their unwanted belongings there, have chamber pots appear for them, etc. But believes he alone can access it at his will.

Therefore, someone going past the door with the sole intent of finding and destroying his horcrux is extremely unlikely. They would have to stumble across the room, making sure it was the room where everything is hidden (rather than da headquarters or chamber pot room), then find the diadem, then destroy it, any singular part of that nearly impossible, which is undoubtedly whyou it was the last one to be discovered.

That is all to say that Voldemort obviously knew people had ACCESSED it, but there is a large difference between access and control. He thought he was the only one to discover how it operated.


I think it was only Harry's assumption that arrogance plays any role here. This assumption is something Dumbledore was teaching him whole year anyway.

The real reason, in my opinion, is that this was supposed to be only temporary hideout. And he knew that the Room of Hidden things is full of random junk. He thought he can come back to Hogwarts any time and pick it up when he has some real hideout for it.

But he never did, because (to his own shock) he lost the ability to even truly care for pieces of his own soul, until he realized they are lost. The last part of Deathly Hallows describes his shock and fear. But for 20 years until then, he probably didn't give his horcruxes a single thought.

  • Problem is: he left it after requesting the job from Dumbledore. Do you really think he would have intended to return to Hogwarts for that purpose? Certainly not easily or any time soon and you note that he wasn't even concerned until he found out about the cup. Then he was still somewhat sceptical that anyone could have found it but what he didn't realise of course is Harry was viewing his very thoughts (I think that's how it went anyway).
    – Pryftan
    Commented Apr 16, 2018 at 23:27

In some sense, Harry Potter did not find it. It was the Voldemort who revealed it through shared visions due to the connection he had made with Potter when he tried to kill Potter. In grand scheme of things, Voldemort never expected people to know that he has created Horcruxes and that too seven of them.

  • Actually he had found it..he had been there before when he was hiding the Prince's book, right? I don't recall if it was the same room they used for DA but either way Harry knew about the room. What he didn't realise until later is he had actually seen the diadem. Perhaps it was even there during DA sessions? Or otherwise when he hid the book? I am pretty sure he had seen it before anyway he just didn't know it was a Horcrux (if he even knew about them yet) not unlike how they didn't know the locket was a dangerous artefact.
    – Pryftan
    Commented Apr 16, 2018 at 23:29
  • Another thing just crossed my mind: Harry only knew it was related to Ravenclaw and the only possible thing that could be thought of was the lost diadem. Harry ended up talking with Helena; Voldemort only made Harry aware it was to do with Ravenclaw.
    – Pryftan
    Commented Jul 7, 2018 at 0:19

The best and in my opinion answer here is that the ROR and the ROHT are distinctly different magical options that the ROR provides and only shows or doesn't show the user what they may see. So, Tom Riddle (at the time, newly crowned Voldemort) sees the ROHT as a place where only he can see. Harry and Draco in later years find all of the contents of the ROHT because, like the Mirror of Erised, they don't care what they find, they are only hiding. Which means, and per Neville's discoveries in DH, the ROR can only provide that which has no loophole.

So in the end, I was one of the people who thought this was a plot-hole, but as always, I was corrected by the HP community. Voldemort's own hubris blocked his knowledge of the ROHT, which so fits into his character arch/ faults.

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