Ngari was a region located in Tibet on Earth.
In 2151, Captain Jonathan Archer claimed that the oldest monastery that he had ever visited – before P'Jem – was in Ngari, Tibet. (ENT: "The Andorian Incident")
According to the Star Trek Encyclopedia, 4th ed., vol. 2, p. 81, it was a Buddhist monastery that Archer visited.
According to Michael and Denise Okuda this monastery should depict the Tholing Monastery, a center for Buddhism established in the 10th century by Yoshi-O, leader of the Guge Kingdom. ("The Andorian Incident", text commentary, ENT Season 1 DVD special feature)