archipelago and island, Estonia, separating the Gulf of Riga from the Baltic Sea. The archipelago's three main islands are Saaremaa, the largest, in the south; Hiiumaa in the north; and Muhu, the smallest, in the east nearest the mainland. Navigable straits separate the islands from each other and from the mainland. Ferries serve the archipelago, and a causeway links the road networks of Saaremaa and Muhu islands.

Muhu island is composed largely of limestone and dolomite. Its main village is Kuivastu, a ferry station on the east coast. Area Muhu island, 79 square miles (204 square km). Pop. (2004 est.) Muhu island, 1,822; archipelago, 45,645.