Kwajalein is one of the world's largest atolls (rings of coral islands). It lies in the Marshall Islands in the central Pacific Ocean. Kwajalein has over 90 islands, with a combined land area of about 6 square miles (16 square kilometers). It is about 190 miles (306 kilometers) in circumference, and surrounds a lagoon with an area of about 840 square miles (2,175 square kilometers).