Northwest of Usakos, rising out of the Namib, is the 2000m (6562ft) Spitzkoppe where there is good mountaineering. Some of the coastal and river areas provide good opportunities for fishing, especially in the waters of the northern Caprivi strip. There are several hiking trails in the Fish River Canyon, the Naukluft Mountains, the Ugab River and the Waterberg Plateau Park. Sandgliding, a pastime popular amongst local people, is available in desert areas. Balloon safaris are organised by some tour operators. Paragliding and sky diving are possible along the coast. There are excellent opportunities for birdwatching, particularly in the Kavango and Caprivi regions. Namibia is home to over 630 bird species. Namibia’s flat terrain and vast open spaces provide good off-road cycling. White-water rafting is popular on the Kunene river, while visitors can join a canoeing safari on the Orange river. Qualified cave divers can explore Dragon's Breath, the world's largest known subterranean lake. A number of operators run horse riding holidays. Travellers looking for more speed can follow one of the 4x4 driving routes across the desert.