The first historic records of Vallisaari date back to 1554, when the first defensive fortifications were built on the island overlooking by the narrow strait at Kustaanmiekka. Fortification work was at its most intense during the Crimean War, when in 1853 these islands became an essential element of coastal defences along the sea approaches to St Petersburg.

Artillery batteries were built here on Vallisaari and nearby Kuninkaansaari, including the formidable Alexander Battery, right in the heart of Vallisaari. The battery’s buildings today lie empty awaiting restoration. Visitors may only enter with special permission, but everyone can get a sense of history by exploring the paths and grassy areas around the fortifications. The platform built over the battery offers superb views of the open waters of the Gulf of Finland to the south, as well as Helsinki’s urban waterfront.