Just off Helsinki, this sea fortress is a UNESCO World Heritage Site. Construction began in the mid-18th century, when Finland was part of Sweden. Visitors find cannons, tunnels, a dockyard and a brewery, as well as several museums, including the Ehrensvärd Museum, the Customs Museum, the Military Museum's Manege and the submarine Vesikko. People live and work here too, and there are galleries, a glass studio, a tea house, a summer theatre, a church and a library.
The HSL ferry runs all year from Market Square, and a waterbus runs from May to the end of September. There are cafés, restaurants, bars, a hostel, a grocery shop and a visitor centre, plus guided tours and a digital guide.
