Chad is divided into multiple regions: a desert zone in the north, an arid Sahelian belt in the centre and a more fertile Sudanesesavanna zone in the south. Lake Chad, after which the country is named, is the largest wetland in Chad and the second largest in Africa. Chad's highest peak is the Emi Koussi in the Sahara, and N'Djamena, (formerly Fort-Lamy), the capital, is the largest city. Chad is home to over 200 different ethnic and linguistic groups. Arabic and French are the official languages. Islam and Christianity are the most widely practiced religions.