The T'Karath Sanctuary from above in 2154
A part of the Sanctuary's interior in 2370
The T'Karath Sanctuary was an historic site located in Vulcan's Forge on planet Vulcan, approximately 37 kellicams south of Mount Seleya. (ENT: "The Forge", TNG: "Gambit, Part II")
During the 2150s, the Syrrannites used the T'Karath Sanctuary as a base to hide from the persecution of the Vulcan High Command. The Sanctuary was hidden from outside observation by the geomagnetic interference inside the Forge and by holographic camouflage. In 2154, Jonathan Archer led T'Pol to the Sanctuary after being given Surak's katra by Syrran.
Shortly after, Administrator V'Las ordered that the Sanctuary be bombarded with photonic weapons, in order to destroy the Syrrannites. During the attack, Archer, T'Pol, and T'Pau were able to find the Kir'Shara in a hidden chamber and escape before much of the Sanctuary collapsed. (ENT: "The Forge", "Awakening")
By 2370, the Sanctuary had been abandoned for centuries, containing only a few decaying ruins and artifacts. The Vulcan Isolationist Movement stored their stolen piece of the Stone of Gol there, and it was where their operative Tallera assembled the entire weapon. She was subsequently captured and the Stone retrieved by Starfleet Captain Jean-Luc Picard. (TNG: "Gambit, Part II")