industries. The archipelago is well known for its Baltic herring and rainbow trout products. Agriculture is limited by the small size and rocky nature of the islands. However, the climate is more favourable than in continental Finland and some islands, particularly Rymättylä, are famous in the nearby continental areas for producing the first new potatoes of the summer. The significance of tourism to the economy of the islands is constantly increasing. The islands are linked by bridges and ferries, and in case of Åland, a small airport. The ferries are divided into two categories: "road ferries" (landsvägsfärja or simply färja in Swedish, lautta or lossi in Finnish) are free of charge and operate mostly on short routes between adjacent (large) islands. They are raft-like in construction and usually operated by the road administration. The small ones are cable ferries (kabelfärja in Swedish, lossi in Finnish), bigger ones do not use cables (and are called lautta in Finnish). The other ferries (förbindelsefartyg in Swedish, yhteysalus in Finnish) are more ship-like in construction, are operated by the maritime administration and may charge a small fee. They operate on longer routes covering several smaller or more distant islands. There are also large commercially operated cruiseferries connecting the Finnish cities of Turku and Helsinki to Åland and Sweden. During cold winters official ice roads are established between some islands. It is also common to drive on ice to islands lacking official ice roads. This greatly eases transportation, as it makes it possible to simply drive a car (or even a heavy van if ice is very thick, usually every few years) from the continent to the islands. On the other hand, during spring and autumn there is a period of thaw (menföre in Swedish, kelirikko'' in Finnish) when the ice is too weak even for walking, but too thick for boating. This can leave some islands lacking a pier for large ships isolated for days or weeks. Access is only by hydrocopter, hovercraft or helicopter. Many important shipping lanes cross the Archipelago Sea. Navigation is made hazardous by the labyrinthine archipelago, varying depth and numerous skerries. For this reason the islands are dotted with lighthouses of varying sizes and navigational marks. Maritime pilot services are maintained by the state. Archipelago Ring Road The most inhabited islands in the eastern archipelago in Southwest Finland are connected by the Archipelago Ring Road. There are approximately of