Paldiski harbour was destined to become an important stronghold in the Russian defence system, and Czar Peter the Great designed the Dutch-type fortifications himself. The fortress with five bastions, located on Pakri peninsula, was cut into the high limestone as one solid construction; the earth walls were 4 m high and 17 m above sea level. In 1790, the fortress had over 40 cannons.

Between 1939 and 1940, oil storage was built in the moat and a railway branch was extended to the fortress; however, the branch was destroyed during the war. During the post-war period, gravel was taken from the earth walls for construction and roads, thus destroying walls between the east and southeast bastions.

Bastions afford a wonderful view of the sea.