The remains of several settlements off the island built by foreign countries demonstrate the importance of Ayutthaya’s intensive trade with many foreign nations. As most of Ayutthaya’s records were destroyed when the city was looted and burned by the invading Burmese in 1767, much knowledge about Ayutthaya’s history was gained from the accounts and maps of foreigners. The Ayutthaya Historical Park was declared a UNESCO World Heritage Site in 1991.