A fortress from the second half of the 19th century (it was built in 1882-1887), located within the Osowiec-Twierdza settlement belonging to the Goniadz municipality, known for its 6.5-month-oldDefense during World War I. At the beginning of the 20th century it was counted among the world's most modern fortresses. Situated in a narrowing of the Biebrza marshes, it was intended to provide cover for the railroad and the Bialystok-Kingdom transport route. The fortress was one of the few that was never captured, and its defense in 1915 went down in history, hence it was compared to the 1916 warfare at Verdun in France. The fortress consisted of 4 forts: the Central Fort - Fort No. 1, Zarzeczny Fort - Fort No. 2, Szwedzki Fort - Fort No. 3 and Nowy Fort - Fort No. 4. Fort 1 (Central), thanks to the activities of the Osowiec Fortification Society (OTF), is now partially open to tourists and has marked routes for sightseeing. The Osowiec Fortress Museum, which is cared for by the Osowiec Fortification Society, is located on the premises of the Central Fort.
26.08.2014