The numerous secret passages in Tallinn’s earthwork fortifications were built along with the bastions in the 17th and 18th centuries. The purpose of the passages was to conceal the movement of soldiers, ammunition and other equipment from the enemy. The passages were also important for reconnaissance – they were used to monitor the enemy’s underground mining activities. The earthwork fortifications were removed from the list of military objects in 1857, and parks were then established on the Ingeri and Swedish bastions. When planning a visit to the bastions please bear in mind that you can only access them with a guide and that the maximum group size is 20 people.