I know that the Valley of the Jedi (or Valley of the Souls) was built by the Jedi Knight, Johun Othone to memorialize the Jedi that gave their lives fighting the Sith in the Seventh Battle of Ruusan. According to the Wookieepedia article on Ruusan (emphasis mine):
...a Jedi Knight named Johun Othone petitioned the Galactic Senate to construct a grand mausoleum containing the one-hundred fallen warriors called The Valley of the Jedi, located on the former location of Olmondo.
And, according to the Olmondo article:
Olmondo was the former capital city of the planet Ruusan.
However, the article on the Valley of the Jedi says this:
The Valley of the Jedi or the Valley of the Souls was the site of the Seventh Battle of Ruusan, the last battle of the New Sith Wars and a thousand years before the Battle of Yavin.
After reading through the events of that battle in the novel, Darth Bane: Path of Destruction, it certainly doesn't sound to me like the thought bomb was detonated in, around, or under a city (even an "abandoned" one). According to that telling of the story:
Lord Kaan led the Sith Lords of the Brotherhood of Darkness into a system of caves to protect themselves from the threat of aerial attacks from Lord Hoth's Army of Light. It was in these caves that the Sith Lord performed the ritual of the thought bomb and detonated it when Lord Hoth confronted them in an effort to ensure that such a weapon wouldn't be used someplace that would result in a greater loss of life.
On the other hand, Wookieepedia also has this to say about the monument:
The Valley of the Jedi then became a concentrated area of Force energy called a Force nexus, and is widely believed to be the most powerful Force nexus in the entire galaxy.
This makes it sound to me like the "remnants" of the thought bomb were in, around, or under the Valley of the Jedi itself, simply because of what those "remnants" actually are. Additionally, according to the Dark Forces novellas, when Kyle Katarn later comes to the Valley of the Jedi to confront the Dark Jedi Jerec, he is able to:
release the imprisoned and tortured spirits of the Jedi and Sith that had been trapped and tortured by the thought bomb's detonation centuries earlier.
There is very little mention of the actual, physical remnants of the thought bomb in those stories, even though much is discussed about its effects. The Bane Trilogy, however, is quite specific about what remained after the thought bomb detonated:
The souls of 100 Jedi and every Sith Lord participating in the ritual were trapped in a silvery ovoid that was created by the ritual and was left over when the thought bomb was detonated. Several characters - Darovit, Zannah, Bane, and others - actually saw or even touched the orb after the detonation.
So, I'm left wondering about the relational positioning of exactly where the thought bomb was actually detonated and the eventual construction site of the Valley of the Jedi. Was the Valley of the Jedi built on top of the site of the thought bomb's detonation, or is/was Olmondo in another location entirely? Please provide source links/references in answers.