This defense tower is often (and incorrectly) referred to as Stockholm's oldest building. According to a myth that spread in the 18th century, it was built during the time of Birger Jarl (Earl Birger, the founder of Stockholm) and named after him. However, an investigation that was carried out in 1917 showed that the tower was built about two centuries later of bricks from the Saint Klara monastery which was demolished in 1527. The tower replaced timbered redoubts destroyed by fire in 1525 and along with the southern tower of the Wrangel Palace, is the only remaining structure from the 16th-century defensive system. Originally, the two towers were connected by a wall.
Source: Wikipedia
Photo: Hasse A.