Peter and Paul Fortress was built as a powerful fortification designed to protect the northern borders of the state from enemy forces.

The military facility assumed the possibility of maneuvering for defensive and offensive purposes. In order to make raids into the enemy camp and enter the enemy from the rear during the landing, underground passages were provided, which were called marches. For these purposes, patterns were also thought out — “invisible” passages in firewalls (the latter were up to 20 meters thick). They were covered with a layer of one brick and imitated a monolithic wall. Trusted people knew about their location.

Currently, the fortress has lost its role as a protective outpost, and a journey through secret tunnels has turned into a fascinating visit to the historical site. The dungeons were illuminated so that everyone could satisfy their curiosity.