During the Great Northern War in 1710, Peter the Great's army took Swedish Vyborg. To protect the annexed territory from enemy claims, defense structures named after Empress Anna Ioannovna were erected in 1730-1750s. The complex complex of four bastions, ravelins and moats had an arc-shaped form, which is why it was nicknamed Annenkron - Anna's crown. This kilometer-long fence never became a place of battles. To this day you can still see the building of the guardhouse, Friedrichsgam and Ravelin gates.