Situated southwest of the Thai capital Bangkok; Phetchaburi is an old royal city; dating back to the ethnic Mon in the 8th century; and later; Khmer settlers. In 1860; King Mongkut (King Rama IV); built a palace near Phetchaburi; that became commonly known as 'Khao Wang'; although its official name is Phra Nakorn Khiri; meaning 'Holy City Hill'. Located on the three peaks of the 92m-high hill are: the king's summer palace; a chedi with a Buddhist temple; and an astronomical observatory. The site was registered as a historical park in 1979; with two of the palace buildings now housing a branch of the Thai National Museum.