In the 15th c, Laos (Ai Lao) usually sent ambassadors to offer tributes to Đại Việt (official name of Viet Nam under the Lê Dynasty). The Emperor ordered to construct a building called Quan Su (Embassy) to receive foreign ambassadors to Thăng Long. Because those ambassadors were all Buddhist, they decided to build a temple on the premises for worship. Today only the temple remains.