Long Ya Men (Chinese: 龙牙门; pinyin: lóngyámén) or Dragon's Teeth Gate, a craggy granite outcrop, formerly stood at the gateway to Keppel Harbour in Singapore. The Long Ya Men served as navigational aids to ancient mariners sailing through the swift waters of the narrow channel between them. The rocks were documented in a navigational map belonging to Ming dynasty's Admiral Zheng He, and also in Wang Dayuan's historical maritime annal, Wu Bei Zhi (武备志). The Long Ya Men's unique features assisted Zheng He in navigating the waters around Singapore during his seven maritime voyages to the west between 1405 and 1433 AD. The rocky outcrops were subsequently destroyed by the British in 1848 to widen the channel for larger vessels to sail through.