Africa contains many diverse landscapes and ecosystems that are home to a wide variety of plant and animal species. Some of the most notable and important natural places in Africa include the Sahara Desert, the largest hot desert in the world; the Nile River, the longest river in the world; and Lake Victoria, the second largest freshwater lake. Other significant landscapes are Mount Kilimanjaro, the tallest mountain in Africa; the Congo Rainforest, the second largest rainforest in the world; and the Serengeti savannah, home to over 2 million large mammals. Madagascar is also notable for its high level of biodiversity, with 90% of plants and animals found nowhere else. The Great Rift Valley