The first fortification structure in this place was built between the years 1811-1813 during the period of the Free City of Gdańsk (Ville libre de Dantzig), being dependent on the French Empire. The decision to build the structure was taken due changes in the shore location of the Gdańsk Bay and moving away of the Fortress Wisłoujście. The structure was seriously damaged by the great flood which hit Gdańsk in 1829. Between the years 1844-46 the Prussians built a new fortification structure (Möwenschanze) in the form of a five-sided telescope (with the open rear), surrounded with a moat and fitted with a reduit on a cross-plan. A drawbridge used to lead to the gate. Between the years 1874-76 Szaniec Mewi was rebuilt to serve as a coast artillery battery. Three stations for 210 mm calibre cannons were placed on the right front embankment. In 1912 the entrenchment was demilitarised. Subsequently, the embankments and the moat were levelled as well as harbour buildings began to be erected. Following the capitulation of Westerplatte on 7th September 1939 Szaniec Mewi became the first temporary prisoner-of-war camp of the captured Polish soldiers. After the Second World War the entrenchment was taken over by the Maritime Office. Until the present day the following elements have been preserved in a relatively good state: the reduit, the wall with the gate (with the remains of the caption ‘MOEWENSCHANZE' and a stone keystone with the inscription "Erbaut 1846"), a powder magazine, a fire station, 210 mm calibre cannon stations as well as bunkers.
Szaniec Mewi is situated within the Navigation Aids Base of the Maritime Office. The facility is not available for visitors. It can be seen from behind the fence. A good observation point is the right shore of Martwa Wisła in Nowy Port. Remains of the entrenchment can also be seen on board ships crossing Martwa Wisła.