King Gustav Vasa ordered the construction of Vaxholm Fortress in 1544 to protect the Swedish capital and mainland. It repelled an attack by the Danes in 1612 and the Russians in 1719, among others. It was a prison from the mid-18th century until 1842. Occupying an islet just east of town, it's now home to a museum and a B&B. The ferry to the island leaves Vaxholm harbour every 20 minutes from 11am to 5pm and costs Skr50 return.
