Alt-Schauenburg is a ruined castle in the commune of Frenkendorf. It is located near the border of France and Germany, and little of the castle remains because of geological events.
There were two Schauenburg castles near Frenkendorf, Alt-Schauenburg about 1 km southwest of the village on the top of Chleiflüeli hill and Neu-Schauenburg to the west. Alt-Schauenburg was probably built around 1275 as the seat of a junior branch of the Schauenburg family. The castle was occupied for less than a century. The 1356 Basel earthquake destroyed much of the castle and shortly thereafter the ruins were abandoned. The ruins were gradually buried, until 1949-50 when they were excavated and repaired. In 1976-77 additional construction helped preserve the site.
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.