Svalbard is an archipelago in the Arctic, constituting the northernmost part of Norway. It is located north of mainland Europe, midway between mainland Norway and the North Pole. The group of islands ranges from 74° to 81° north latitude (inside the Arctic Circle), and from 10° to 35° east longitude. Spitsbergen is the largest island, followed by Nordaustlandet and Edgeøya. The administrative center is Longyearbyen, and other settlements include the Russian mining community of Barentsburg, the research community of Ny-Ålesund and the mining outpost of Sveagruva. The archipelago is administered by the Governor of Svalbard. The islands were first used as a whaling base in the 17th and 18th centuries, after which they were abandoned. Coal mining started at the beginning of the 20th century, and several permanent communities were established. The Svalbard Treaty of 1920 recognizes Norwegian sovereignty, and the 1925 Svalbard Act made Svalbard a full part of the Kingdom of Norway. This act also established Svalbard as a free economic zone and a demilitarized zone. The Norwegian Store Norske and the Russian Arktikugol are the only mining companies remaining on the islands. Research and tourism have become important supplementary industries. Two major research facilities are the University Centre in Svalbard and the Svalbard Global Seed Vault. No roads connect the settlements; instead snowmobiles, aircraft, and boats serve inter-community transport. Svalbard Airport, Longyear serves as the main gateway to the rest of Europe.