B'hala was a Bajoran holy city that was lost for twenty thousand years.
Sometime after the founding of the city, a battle between Gorgan and Lady Q occured above the skies of Bajor. Gorgon attempted to flee through the wormhole but was stopped by the Prophets, the resulting battle between Gorgon and Lady Q resulted in a "five dimensional" light show over the skies of B'hala which lasted for 1000 days. The Kai of Bajor at the time was at a loss to explain what was occuring and some of her Vedeks believed it was the Reckoning - a claim she disproved since the Emissary had not yet been chosen. (TNG novel: Q-Strike)
In the alternate timeline of the War of the Prophets, a rock which contained advanced passive sensors was sent to the time of the formation of the city by Kai Weyoun through the Orb of Time in order to locate several Deep-time charges that Starfleet had sent through a timeship in order to cripple the Bajoran Ascendancy in the future. (DS9 - Millennium novel: The War of the Prophets)
By 2376, the archaeological teams still consisted largely of Bajorans, such as Prylars Eivos Calan and Krish, but also included some offworlders such as a team of Vulcan chronologists. The teams included highly experienced individuals down to new students. Student positions were meant to only be offered to religious initiates however when Jake Sisko visited the site that year the Order of the Temple offered him a position which he quickly accepted. Jake worked on the site for the first few months of 2376. It was there that Jake learned of the Prophecy of the Avatar from Prylar Istani Reyla, who had recently discovered the lost prophecies of Ohalu.
A short while later, following an orb experience Kira Nerys led a small party to B'hala and near where Istani found the prophecies discovered a mass tomb, holding the ten thousand bodies of the individuals who had guarded Ohalu's prophecies. (DS9 - Avatar novels: Book One, Book Two)
Benjamin Sisko joined the archaeological team excavating B'hala in 2379, after the death of Eivos Calan. Sisko did so out of respect for the man who he had become friends with. (ST - Typhon Pact novel: Rough Beasts of Empire)