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:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.