The Mannar Dutch Fort, located on Mannar Island, was originally built by the Portuguese in 1560 and later rebuilt by the Dutch in 1696. The fort has a square shape with four bastions and is currently occupied by the Department of Archaeology. It stands as a historical landmark that showcases the colonial history of the region, attracting visitors with its well-preserved structure and picturesque location next to the new bridge connecting the mainland with Mannar Island.