Peter the Great's Naval Fortress or the Tallinn-Porkkala defence station was a Russian fortification line, which aimed to block access to the Russian capital Saint Petersburg via the sea. The plans for the fortress included heavy coastal artillery pieces along the northern and southern shores of the Gulf of Finland. The emphasis was put on the defenses of the gulf's narrowest point, between Porkkala, (in current day Finland) and Tallinn, (in current day Estonia). This was a strategic point, as the two fortresses of Mäkiluoto and Naissaar were only 36 kilometers apart. The coastal artillery had a range of about 25 kilometers and could thus "close" the gap between the shores, trapping enemy ships in a crossfire. Furthermore, a new major naval base was constructed in Tallinn.