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.