Trincomalee Harbour is in Koddiyar Bay, a large natural harbour situated on the northeastern coast of Sri Lanka.Located by Trincomalee, Sri Lanka, in the heart of the Indian Ocean. There have been many sea battles to control the harbour. The Portuguese, Dutch, French, and the British have each held it in turn. In 1942 the Imperial Japanese Navy attacked Trincomalee harbour and sank three British warships anchored there.The harbour, one of the largest natural harbours in the world, is overlooked by terraced highlands, and its entrance is guarded by two headlands.