The castle in Koźle was probably built during the location of the city, that is at the beginning of the 14th century. In the years 1282-1355 it was the capital of the independent Koźle duchy, remaining in the hands of the Opole Piasts. In the late Middle Ages, the castle lost its importance, and in the sixteenth century passed into private hands. Already in 1558, it was uninhabitable, which caused a thorough renaissance reconstruction in the years 1563-1583. In the 18th century, the whole town and castle complex was transformed by the Prussians into a great modern fortress. An older building was destroyed then.
The medieval castle was situated on an artificial mound and built of brick on stone foundations. It was an object on a square plan with a side of about 50 meters with rounded corners. In the middle of the courtyard there was a free-standing, four-sided residential tower, which is the oldest element of the castle. The circumference of the defensive walls was strengthened by a four-sided tower in the south-east corner of the walls. The remaining buildings of the courtyard were wooden. During the sixteenth century reconstruction, four-sided bastion was added to the south-west corner, and the main residential house was erected by the eastern curtain. In the seventeenth century, the southern wing was added. The castle had a outer bailey.
To this day, fragments of the perimeter walls, fragments of two wings of the castle and the foundations of the tower have been preserved, which has been recently rebuilt in a stylized form.
Leksykon zamków w Polsce, red. L.Kajzer, Warszawa 2003.