Doboj Fortress or “Gradina” is located in the city of Doboj.
One of the most important defenses in the medieval bannate/duchy of Usora, this large stone structure was built in the early 13th century on the site of an earlier, clay and wood-based structure from the 10th or 11th century. In the first period of its existence, from early 13th to about early 15th century (1415), the fortress was built in the Romanesque architecture style. Throughout its turbulent history, this magnificent object has been burned and ransacked at least 18 times as per official records. Of note is that Doboj fortress was considered to be a royal Kotromanic property, unlike Great Bosnian Duke Hrvoje’s Zvecaj fortress or Sandalj Hranic’s Blagaj fortress, which were centers of their respective dukedoms.
Doboj fortress underwent a major reconstruction in the spring of 1415. While still retaining some of its original Romanesque elements, the fortress now displays Gothic structure and had its large keep reinforced with thick walls (up to 3 feet or about 1 meter thick at the Eastern wall) as well as having an addition of a bastion/plateau with six cannon on top of it. The captain’s tower was turned into even more dominating feature with several stories tall square keep towering over the fortress. Additional outer walls were added around the original triangular core and three big towers (North-West, Eastern, and Southern Gate) have been strengthened as well. These towers strategically protect flanks of the fortress, hence rendering any idea of an attack a suicidal attempt. The Southern tower’s walls, in particular, are changed into round shape in order to deflect cannonballs (circa 1370-1380s) and local captains at the time used Dubrovnik-made cannons, bombards, and balistas as fortress’ main defense weaponry (Dubrovnik was known as Republic of Ragusa at the time).
Despite some damages suffered from shelling during the Bosnian War, the fortress is very well preserved. In the late 2000’s, it could be visited and was properly maintained. However, since the 2010s, the regular maintenance was abandoned and the castle was vandalized while the facilities gradually fell in decay. In 2016-2017, new works took place in partial conservation of the fortress along with new archeological diggings revealing medieval arrowheads, pieces of clay and glass and decorative pottery, and both elements of crude and fine metal work. The lower layers of three flanking towers, in particular, remain inadequately researched with much more potential for future digs and detailed and long lasting conversation of this historical structure.