Widely regarded as the second largest canyon in the world after the USA's Grand Canyon, the Fish River Canyon is located in southern Namibia in the eastern Namib Desert. The 100-mile (161km) long canyon was caused by a fracture in the earth's crust and then further carved by the erosion of the Fish River over millions of years. The river can still become a torrent of fast-flowing water after heavy rainfall in summer, but dries up into occasional semi-permanent pools during the winter months. The main attraction of the area is hiking, but hiking the Fish River Canyon can only be undertaken during the winter months, requires a high level of fitness and good health and offers no facilities whatsoever. The five-day trail covers 53 miles (86km) and is the best way to take in the canyon's magnificent immensity, passing beneath the sheer cliffs with their visible rock strata patterns towering 1,640ft (500m) above the harsh, rock-strewn plain. The canyon comes to an end at Ais-Ais (meaning 'burning water' in Nama) where one of the most famous hot spring resorts in the country is located, and hikers can look forward to a relaxing soak in the therapeutic hot water after completing the trail.