ShiGral

ShiGral was a legendary city from Vulcan prehistory. It was supposedly founded by Surak prior to the Time of Awakening, and stood as an oasis of logic and peace during Vulcan's violent era. ShiGral was said to have been the only place where Surak's ideals were ever fully realized, and that, if Vulcan were to stray too far from his teachings, Surak would return to ShiGral.

By the 23rd century, ShiGral was widely considered to be a myth, and a majority of Vulcans did not believe in its existence. Despite this, a team from the Federation Archaeology Council was sent, circa 2293, to Vulcan to dig for the city on a site near the Llangon Mountains. This project was abandoned in 2293. (TOS short story: "The First Law of Metaphysics")