The mysterious passages in Tallinn’s earthwork fortifications were built along with the bastions in the 17th and 18th centuries in order to conceal the movement of soldiers, ammunition and other equipment from the enemy. Tthey were also used to monitor the enemy’s underground mining activities. After the fortifications were removed from the list of military objects in 1857, parks were established on the Ingrian and Swedish bastions.
In the bastion's passages, a train to the future takes you to the year 2219, another one takes you back to the 17th century. Passages are only accessible with a guide; the size of the group is a maximum of 20 people. Tunnel leading to the passages is lined with columns introducing various calendars.