The state's most visited attraction, the Oregon Zoo is home to over 1,000 animals representing 200 species of birds, mammals reptiles and amphibians, including 54 that are threatened or endangered. Its outdoor habitats and modern indoor pavilions are spread over 64 forested acres. Five new exhibits are collectively called The Great Northwest and introduce visitors to the animals found in habitats ranging from the Cascade Mountains to the rocky shores of the Pacific Ocean.The zoo is famous for its Asian elephants, one of the largest breeding herds in the world. Since 1962, 28 calves have been born in the zoo. The four-acre Africa Plains exhibit replicates the dry, open bush country of East Africa and features rare black rhinos, Nile hippos, giraffes and naked mole-rats. Housed in their own building, these tiny African animals with permanently closed eyes inhabit a warren of underground tunnels with glass-sided viewing areas. The impressive Alaska Tundra exhibit re-creates the harsh environment of Alaska's North Slope, while the popular indoor Penguinarium is home to a colony of endangered Peruvian Humboldt penguins and a flock of Inca terns.