The Navajo Nation (Navajo: Naabeehó Bináhásdzo) is a semi-autonomous Native American territory covering 27,425 square miles (71,000 km2), occupying portions of northeastern Arizona, southeastern Utah, and northwestern New Mexico in the United States. This is the largest land area retained by a U.S. tribe and is managed via agreements with the United States Congress as a sovereign Native American nation. The Nation has a government that includes a legislative house, an executive office, and a judicial system. The executive system manages a large law enforcement and social services apparatus, Health Services, Diné College, and other local educational trusts. It founded a Navajo Zoo at Window Rock, which in 2016 opened its Eagle Aviary and Education Center.