“Do you see the spot where the Duburg once stood?” I ask. “Right here in Flensburg this imposing castle once dominated the skyline. Built in 1411 by order of Queen Margarethe I of Denmark it was a formidable structure a testament to Danish power in this strategic location. Its purpose was clear to control Flensburg a rich and important trading hub. The Duburg wasn’t just a castle it was a key part of Flensburg’s defenses. It wasn’t part of the city itself until 1875. Before that it belonged to the parish of Handewitt. Think of it a strongpoint guarding the city.
The Duburg’s strategic importance is evident in the many sieges it withstood. In 1412 Erich Krummediek tried to take Flensburg but failed against the still-under-construction Duburg. Later in 1422 and 1427 more attacks failed. The Hanseatic League itself laid siege. This siege lasted two weeks. The attackers finally succeeded only in 1431. Even then the Duburg held out until September. The castle only fell through starvation after a combined sea and land blockade.
The castle’s name is intriguing too. Some believe it’s named after Jens Due a high-ranking Danish official involved in the Duburg’s construction. Another theory links the name to the Danish word for “dove” due. Over time the castle became known as Duburg in German and Duborg in Danish.
The Duburg was massive. Jakob Röschmann estimates its area at 200 by 250 meters. It had extensive fortifications a moat a wall and even a palisade-protected passage called the “Bart” leading to the harbor. From this vantage point the Duburg would have commanded a spectacular view. Imagine the awe it inspired in those who saw it standing tall.
Despite its strength the Duburg eventually fell into disrepair. By 1523 it was in a terrible state. Three years later however Herzog Adolf was born within its walls. The construction of Glücksburg Castle in 1582 marked a shift in power. Glücksburg was more representative but less strategically important than the Duburg. Yet the Duburg still served as a royal residence until 1719. King Christian V was even born there in 1646. King Karl X Gustav of Sweden also stayed there for several weeks in 1658 during the occupation of Flensburg.
In 1719 King Friedrich IV ordered the Duburg’s demolition. The stones were donated to the Flensburg orphanage. They went to build the orphanage. The Flensborghus now stands as a testament to this. Some of the larger bricks can still be seen. The southeastern corner remained until 1898 when it was demolished for urban development. Even then some of its stones ended up in another landmark the Erlkron tower ruin in Glücksburg. Today only the Schloss-Duburg-Schule a school stands where this magnificent castle once stood. A commemorative plaque reminds us of its legacy. So next time you are here think of the mighty Duburg a powerful castle a silent guardian of Flensburg’s history. A significant part of the town is named after the Duburg. Don’t forget this piece of the Duburg story.
”