The Middle East and North Africa share many characteristics. Islam is the dominant religion and Arabic is widely spoken. Most of the region is desert with little rainfall. However, there are exceptions like Iran where Farsi is spoken. The oil wealth of some nations has led to modernization while others have used wealth to build strong militaries. The Suez Canal and Nile River are important waterways but the Aswan Dam has had environmental impacts by preventing flooding and silt deposition.