Ayutthaya (full name Phra Nakhon Si Ayutthaya, Thai: พระนครศรีอยุธยา, pronounced [pʰráʔ na.kʰɔ̄ːn sǐː ʔa.jút.tʰa.jāː]; also spelled "Ayudhya") is the former capital of Phra Nakhon Si Ayutthaya province in Thailand. Located in the valley of the Chao Phraya River, the city was founded in 1351 by King U Thong, who went there to escape a smallpox outbreak in Lop Buri and proclaimed it the capital of his kingdom, often referred to as the Ayutthaya kingdom or Siam. Ayutthaya became the second Siamese capital after Sukhothai. It is estimated that Ayutthaya by the year 1600 CE had a population of about 300,000, with the population perhaps reaching 1,000,000 around 1700 CE, making it one of the world's largest cities at that time, when it was sometimes known as the "Venice of the East".