The Stockholm archipelago is the city's natural defense against the sometimes capricious Baltic Sea. The number of islands that are included in the archipelago is the subject of eternal debate. It is estimated that about 24,000 islands make up the Stockholm archipelago. Almost all the islands are well connected to the city by regular lines of boats and ferries. That makes them attractive to visitors who live just a few kilometers from the center of Stockholm, one of the largest cities in this part of the world, and find pastures, farms, wooden houses, and complete peace.