Micronesia is a subregion of Oceania, consisting of approximately 2,000 small islands in the Northwestern Pacific Ocean. It has a close shared cultural history with three other island regions: Maritime Southeast Asia to the west, Polynesia to the east, and Melanesia to the south—as well as with the wider community of Austronesian peoples. The region has a tropical marine climate and is part of the Oceanian realm. It includes four main archipelagos—the Caroline Islands, the Gilbert Islands, the Mariana Islands, and the Marshall Islands — as well as numerous islands that are not part of any archipelago. The city of Palikir is the capital; English is the official language; and the U.S. Dollar is the national currency.