Søborg Castle, in its heyday, was the strongest castle in Denmark, and was also used as a prison. It was inhabited until the Count's Feud in 1535, when it is speculated that it was destroyed. In 1577, the feudal tenant was granted permission to use the ruins as a quarry.
Søborg Castle is first known from the 12th century, when ownership of the castle passed from the king to the bishop of Roskilde. Traditionally archbishop Eskil of Lund is said to have expanded the previous buildings to a real castle with defensive walls and a moat. As Eskil was in close contact with Esrum Abbey, it is considered likely that he lived nearby at Søborgby.
In 1985, Robert Egevang and Søren Frandsen took the initiative of digging two trenches to make clear the conditions between the octagon tower and the castle proper. A rampart approximately 11 meters wide is the oldest encirclement of the castle. In the rampart, as well as in the octagon tower which was built at the same time, tiles have been found. The excavations show that the castle proper was erected in the late 13th century, which would make it unlikely that Eskil was the builder, as he died in 1181. The tiles are very unevenly made, evidence of their novelty in Denmark, after having only recently arrived from Lombardy.
In the Middle Ages, the castle was on an island in a fjord with an outlet to the Kattegat by Gilleleje. Later, the fjord became Søborg Sø, which was drained 1872-1896 when a canal was dug to Gilleleje.
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.