Could a Portkey be used to travel from one place in Hogwarts to another?

Question

What I need to know is whether or not someone that is already inside Hogwarts could create a Portkey to take them to a specific location in Hogwarts. So, let’s say they’re in the Potions classroom; they reach into their pocket, touch the Portkey, and it takes them to the Astronomy tower.

I’ve seen several questions here about Portkeys being made to travel into Hogwarts and out of Hogwarts, but none about Portkey travel inside Hogwarts. The aforementioned questions seemed to lead to the theory that only the headmaster could create a Portkey to travel to and from Hogwarts, though apparently nothing about Portkeys and Hogwarts is stated clearly in canon: only that Apparating to and from Hogwarts is impossible.

It seems to me that the magical barriers surrounding Hogwarts would only protect from travel into and out of the grounds, and that the use of Portkeys inside Hogwarts wouldn’t be detectable. I’ve also read that Portkeys have to be authorized by the Ministry, but fans seem uncertain as to whether or not the Ministry has anything set up to detect the use of unauthorized Portkeys, so I’m overlooking it at the moment; but, if any new info has come out about that, I’d appreciate a heads up.

(Edit): Some examples of other questions I’ve seen concerning Hogwarts and Portkeys on this site and others:

-This one (from Reddit) says more about my mention of the theory that the headmaster is an exception, as well as laying a bit of doubt on the idea that Barty Crouch Jr. was the sole reason the Triwizard Cup was a Portkey: https://www.reddit.com/r/AskScienceFiction/comments/3g2wqy/harry_potter_do_portkeys_work_at_hogwarts/

-From SciFi Stack: why was the triwizard cup used as the portkey & why couldn’t Voldemort use a portkey to enter Hogwarts

Answer 1

Yes

There are (at least) four examples of Portkey usage that involve travel out of, or in to, Hogwarts within the books. These are:

1. Hogwarts (Quidditch pitch, inside maze) -> Little Hangleton (graveyard) in Goblet of Fire
2. Little Hangleton (graveyard) -> Hogwarts (Quidditch pitch, outside maze) in Goblet of Fire
3. Hogwarts (Headmaster's office) -> Grimmauld Place in Order of the Phoenix
4. Ministry of Magic -> Hogwarts (Headmaster's office) in Order of the Phoenix

None of those examples are explicitly Hogwarts to Hogwarts. However, if we consider the original intention for Goblet of Fire - i.e. the state of affairs without Barty Crouch Jr. setting up additional Portkey to send Harry to Voldemort - then it would have simply been Hogwarts (Quidditch pitch, inside maze) -> Hogwarts (Quidditch pitch, outside maze).

I'll note here that while it's never explicitly stated that the Triwizard Cup was a Portkey, it's consistent with the events that actually occur, and makes sense as a means of proving who actually touched the Cup first (which was when the third task officially ended).

Answer 2

Yes.

Since this has never been tried in canon (so far), we can only speculate. However, there are a few relevant facts that I think indicate it's indeed possible.

1. You can travel into and out of Hogwarts by Portkey. As you mentioned, this has been done by Dumbledore (but also a few others of dubious canonicity, like Zygmunt Budge's Book of Potions which is usable inside Hogwarts). Arguably it's also been done by Crouch Jr., who modified Dumbledore's Portkey to travel out of Hogwarts and back into it.

2. You don't need special permission to create a Portkey. Although Remus Lupin warns Harry ominously against creating an unauthorized Portkey, Dumbledore does it right in front of Cornelius Fudge, because he DGAF:

[Dumbledore] walked away from the pool to the place where the golden wizard's head lay on the floor. He pointed his wand at it and muttered, "Portus." The head glowed blue and trembled noisily against the wooden floor for a few seconds, then became still once more.
"Now you see here, Dumbledore!" said Fudge, as Dumbledore picked up the head and walked back to Harry carrying it.
_{Harry Potter and the Order of the Phoenix, Chapter 36}

For even more direct proof that Ministry permission isn't required, Newt Scamander pays handsomely to transport himself and Jacob Kowalski internationally via illegal Portkey.

3. Hogwarts isn't protected against all unauthorized transportation-- just Apparition. We learned this in The Half-Blood Prince, when Draco Malfoy successfully creates a (very unauthorized) Vanishing Cabinet that allows Death Eaters to infiltrate Hogwarts.

So to summarize, since Hogwarts seems to allow Portkeys, and there's nothing stopping you from creating one (aside from the law), I think this is definitely possible.