Schloss Hollenburg is a medieval castle near Köttmannsdorf. It is on a rock of the northern slope of the Drava valley. One Swiker, Lord of Hollenburg in the Duchy of Carinthia was first documented as a witness in the 1142 deed of the foundation of Viktring Abbey. He may have been a liensman of the ducal House of Sponheim; his son Reginher is mentioned as Lord of Steuerberg, he accompanied King Conrad III of Germany on the Second Crusade in 1147 and later appeared as a ministerialis of Margarve Ottokar IV of Styria.
The castle was of strategical importance due to its location at a Drava river crossing and the road to the Loibl Pass and the March of Carniola. Upon the extinction of the Hollenburg dynasty in 1246, it passed to the Styrian Lords of Pettau, in 1438 it was inherited by the House of Stubenberg. The structure had been severely damaged by the 1348 Friuli earthquake.
In 1514 the Habsburg emperor Maximilian I, stuck in the War of the League of Cambrai against Venice and highly indebted, sold Hollenburg to Lord Siegmund of Dietrichstein, elevating him to the rank of a Freiherr (Baron). The House of Dietrichstein had the castle rebuilt in a Renaissance style, finished in 1588. The Dietrichsteins held the castle until the extinction of the branch in 1861, it was acquired by the Wittgenstein family in 1913.
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.