Nawiliwili is on Kauai island, north-western Hawaii, situated north-west of Oahu, from which it is separated by the Kauai Channel, and east of Niihau, from which it is separated by the Kaulakahi Channel. The state's fourth-largest island, sometimes known as the Garden Island, it was formed by volcanic action and is covered with mountains, the highest being Kawaikini Peak, rising to 1,599 km (5,243 ft) above sea level. Kauai is seamed with canyons, the deepest of which, Waimea, is almost 16 km (10 mi) long and more than 0.8 km (0.5 mi) deep. The main population centres are Lihue and Kapaa and there is an excellent beach at Kalpaki