The Galle Fort, or Dutch Fort as it is also known, is a fortification first built by the Portugese on the Southwestern coast of Sri Lanka. The initial fortifications, which were built in the late 16th century, were quite basic. However the fort underwent extensive modifications in the 17th century by the Dutch, making it one of the most important archeological, architectural and historic monuments to illutrate the European influence in South East Asia between the 16th and 19th centuries. According to a statement by UNESCO the site was recognized as a World Heritage Site for its unique exposition of an urban ensemble which illustrates the interaction of European architecture and South Asian traditions from the 16th to the 19th centuries which is the criteterion number four for such recognition.
If you have time, I do recommend checking it out- the water is gorgeous and the view is breathtaking.