Osowiec Fortress also known as Osowiec Castle or Osowiec-Twierdza, was a military fortress in Poland that played a significant role in the country’s history. It was located in the Podlaskie Voivodeship (province) in northeastern Poland, near the border with Belarus. The fortress was built in the late 19th century as part of the fortification system of the Russian Empire, and it served as a key defensive point against potential attacks from the west.

The fortress played an important role in the defense of Poland during World War I and World War II. In 1914, at the outbreak of World War I, the fortress was captured by the Germans and was used as a military base and prison. During World War II, the fortress was occupied by the Germans and was used as a training ground for their troops. It was also used as a detention center for prisoners of war and as a location for executions.

After World War II, the fortress was used by the Soviet Army as a military base. It was eventually abandoned in the early 1990s and fell into disrepair. In recent years, efforts have been made to restore the fortress and turn it into a museum. Today, the Osowiec Fortress is a popular tourist attraction and a symbol of the history and defense of Poland.