Pho Phi (Thai: เพชรบุรี; English: PhetchaBuri), or simply Muangphetch, is an ancient city with a long history. During the Sukhothai and Ayutthaya periods, Pho Phi was already an important city in the west and was a major border town of the Ayutthaya Kingdom against Burmese invasions. The city has been ruled by the royal lineage. Ancient ruins and artifacts can be found throughout the city. The city covers an area of 6,225 square kilometers, with high forested mountains in the west, which is the natural boundary between Thailand and Myanmar, and 80 kilometers of coastline in the east, up to the Gulf of Siam.