The Poterna is so called patrol passage (French poterne in a fortresses was used as a closed gallery passage) was an integral part of the Second defensive bank which encircled Koenigsberg with 15-kilometer ring in 1843-1850.

During the postwar period the Poterna was neglected and used as a warehouse; step by step it was going into ruins. In 2005 this construction was passed to the Museum of the World ocean for restoration.

Bricks of the defensive bank and the “patrol passage” are protected with ceramic crust. But it was found that even solid materials were not eternal. Moreover, joints in the brickwork were made with simple (non-waterproof) composition. It led to vulnerability of construction and a serious restoration was needed. Despite zero level of the “patrol passage” floor, brickwork was in a zone of humidity, joint composition was covered with moss and plaster fungi. Bricks were cracked and water penetrated into them. In the winter water froze and damaged bricks. Rootage also destroyed the bank.

Restorers strengthened the arches, impregnated brickwork with special solution, sandpapered the bricks and made their colour even with special compositions.

Restoration works were completed in April 2008.

Nowadays a new exhibition hall “Stories from the Sea Bottom” devoted to undersea archeology will be created in the Poterna.