The Okavango Delta is located where the Okavango River reaches the central part of the endorheic basin of the Kalahari at a tectonic trough. It is a large, swampy inland that was the 1000th site to be included in the UNESCO World Heritage List. Due to its magnificence and scale, it was included in the Seven Natural Wonders of Africa in 2013. The delta has many islands, the largest of which is Chief’s Island which is 70 kilometers long and 15 kilometers wide. When the waters rise, this is where much of the wildlife gathers. Many of the smaller islands are formed of salt which gathers at the roots of plants and then eventually forms an island. Okavango Delta is home to 71 species of fish and the most populous large mammal is the lechwe antelope.