Srebrna Góra Fortress was constructed in 1765–1777 when the territory was part of the Kingdom of Prussia. The fort is one of Poland's official national Historic Monuments and has been declared a rare example of a surviving European 18th century mountain stronghold.
The fortress in Srebrna Góra was built by the order of Frederick II, the King of Prussia. It was designed by Prussian architect Ludwig Wilhelm Regeler, aided by a number of Prussian military engineers. Minor additional works took place in the following years, but no major alterations were made; construction of a nearby flanked fort was begun but was quickly abandoned. The complex is composed of six forts, several bastions, and associated elements. The main fort of the complex is the central Donżon Fort on the Warowna Góra hill.
The complex is located on the heights of the Sudety Mountains, a body which forms a natural border between the Kłodzko Valley and the Silesian Lowlands. It controls the passage through the Silver Valley (Przełęcz Srebrna or Silberbergpass). The fort could shelter a garrison of 4000 soldiers, supplied to survive a year-long siege. It was defended by 264 artillery pieces. The fortress was intended to guard a route linking Prussian territories with Bohemian lands in the south, and thus help repel any possible incursions from Austria.
The fortress was never captured by the enemy while besieged. On 28 June 1807 it successfully resisted a siege by Napoleonic forces during the War of the Fourth Coalition; this was the only time the fortress was the site of an active battle. By 1860 it was declared obsolete and the garrison reduced in size; it was abandoned as an active military stronghold in 1867. The fortress has survived till modern day with relatively little modernization or damage, contributing to its valuable status as a historical monument of its era. It served as a military training grounds, and by the end of the 19th century was already a tourist attraction, with a restaurant opened in the fort by 1885.
During World War II the fortress was used as a prison for Polish officers imprisoned by the Germans. In 1973 a military museum was opened in the Fort.
References:Sigmaringen Castle was first mentioned in the year 1077 in the chronicles of Petershausen monastery. The oldest parts of the castle are concealed beneath the alterations made during the 17th and the 19th centuries. The secret of the earliest settlement built on this defendable rock will never be fully revealed: large-scale excavation work would be necessary, which the extensive land development renders impossible. Judging from the many Roman remains unearthed in the area around Sigmaringen, the 12th century keep known as the 'Roman Tower' could be traced back to a Roman predecessor.
The castle remains that have been preserved (gate, great hall and keep) date back to the Staufer period around 1200. The castle remains were integrated into subsequent buildings. The foundations of the castle buildings are to a large extent identical to the surrounding castle wall.
These remains give us a good idea of how the castle might have looked during the 12th century.