Fish River Canyon, Namibia

Fish River Canyon is one of Africa's greatest natural wonders — a colossal gash in the earth's crust that plunges 550 metres into the arid southern Namibian plateau. At 160 kilometres long and up to 27 kilometres wide, it is the largest canyon in Africa and the second-largest in the world after the Grand Canyon. The scale is overwhelming: layer upon layer of ancient sedimentary rock folded, fractured and carved over 500 million years by the Fish River, which now flows as little more than a trickle through the canyon floor. The main viewpoints — Hobas and Hell's Bend — perch on the northern rim, offering vertiginous panoramas of the canyon's serpentine curves, ochre walls and the thread of green vegetation far below. For serious hikers, the Fish River Canyon Hiking Trail is Namibia's most celebrated multi-day trek: an 85-kilometre, five-day wilderness route that descends into the canyon and follows the riverbed to Ai-Ais, where natural hot springs await weary legs. The trail is open only from May to September (when temperatures are bearable), and hikers must be fit and self-sufficient — there are no facilities, only the river, the rock and the sky. For those who prefer to stay on the rim, scenic drives, short walks and sunset viewing offer a taste of the canyon's grandeur.