On 6 September 1503, by the order of Grand Duke of Lithuania Alexander Jagiellon, the construction of the Vilnius defensive wall started at the expense of Vilnius burghers. The wall formed a closed circle, almost two and a half kilometres in perimeter, around the entire city.

The height of the wall in some places reached ten or twelve metres, and the thickness varied from two to three metres. Nine gates were built in the wall. The construction was finished in 1522, and later, in the first half of the 17th century, a bastion was built in the wall next to Subačiaus Gate. It was a defensive structure consisting of a tower, a horseshoe-shaped part meant for the artillery, and a connecting tunnel. The bastion suffered greatly in 1655–1661 during the war with Russia. Although it was subsequently rebuilt, the defensive structure gradually lost its function, was abandoned and fell into decay. In the late 18th century, the bastion territory was turned into a city dump, its moats were filled up and its walls were covered with earth.

Only the legends about a basilisk that lived in the bastion and an underground tunnel connecting the Vilnius and Trakai castles survived. The renewed exhibition offers the visitors to take a close look at this monument of architecture, presents the history of the defensive castle of Vilnius and the armaments of that time.