From 1479, the Thierstein family began work on the Haut-Koenigsbourg castle. The brothers Oswald and Guillaume were entrusted with the modernization of the fortress, which they enlarged and adapted to the latest military techniques. A double belt of walls, flanked by towers, was equipped for the shooting of firearms. On the mountainside, the brothers built a fortified bastion. These modern defenses did not prevent the Haut-Koenigsbourg from falling into the hands of the Swedish army after 52 days of siege in 1633. Looted and set on fire, the castle remained unoccupied for more than two centuries.