PHETCHABURI

Phetchaburi is an old royal city, In 1860 King Rama IV built a palace near the city of Phetchaburi, commonly known as Khao Wang, but its official name is Phra Nakhon Khiri. Next to the palace the king built a tower for his astronomical observations.
https://www.tourismthailand.org/About-Thailand/Destination/Phetchaburi