Ayutthaya, Thailand

Ayutthaya was founded in 1350 AD and became the capital of the second kingdom of Siam by a king who went to the city to escape a smallpox outbreak in the city Lop Buri. The city was a large city, estimated to have 1 million people by the year 1700 and was a trade hub in southeast Asia. In 1767, the city and kingdom were destroyed by the Burmese.
People fled the city and formed Bangkok as the capital. Today, the Aytthaya ruins are a UNESCO World Heritage Sight.