At a glance, this might look like some ordinary swamp, but the Okavango Delta in the African nation of Botswana is a veritable miracle of nature. Unlike most rivers, the Okavango River doesn"t drain into any sea or ocean, but rather empties into the open savanna. Thousands of elephants, and just about every other type of African animal you can name, owe their existence to this annual wetland. "Annual," because the marshland of the delta swells threefold to its full size but once a year, between March and July, when the seasonal rains from the highlands of Angola flow downhill 750 miles until they flood the arid savanna of northwest Botswana. The wildlife drawn to this life-sustaining water includes lions, leopards, cheetahs, rhinos, giraffes, zebras, hippos, wildebeests, hyenas, crocodiles, impalas, and of course elephants, the planet"s largest land animals.