The Royal Botanical Gardens are located south of Kandy at Peredeniya on the banks of the Mahaweli Ganga. The gardens were first planted and laid out for King Kirthi Sri Rajasingha (1747-1780) and cover 150 acres with lawns, flowering shrubs and in excess of 10,000 trees and 4,000 plant species. During British rule, the royal park became a botanical garden in 1821. Here exotic crops such as coffe, tea, rubber and cinchona (quinine) were all tested and now form a large part of the islands economy. The gardens were the headquarters of the head of the Southeast Asia Command, Lord Mountbatten during the second world war and later the setting for some of the scenes for the film Bridge Over the River Kwai, which was filmed on the island.