Podbolesławiec Castle, Medieval castle ruins in Bolesławiec, Poland.

Podbolesławiec Castle consists of the surviving stone walls and foundations of a medieval fortress situated beside the Prosna River. The remaining structures allow visitors to understand how the defensive layout was organized and to appreciate the scale of the original construction.

A wooden stronghold existed near Bolesławiec by around 1266, recorded as Boleslawecz in 1268. The brick castle was probably begun before 1340 under Casimir the Great, as chroniclers Janko of Czarnków and Jan Długosz attest. In 1370 Louis of Hungary granted it as a fief to Władysław Opolczyk, who enlarged it around 1390 with an octagonal brick bergfried about 22 m high. Władysław Jagiełło besieged it in 1391 or 1393 without success, and recovered it in 1401.

The ruins demonstrate how medieval communities organized their defenses and built structures to withstand attacks. Walking through the site reveals the practical choices builders made when constructing a fortress in this region.

The ruins stand on an artificial mound about 9 metres high on the western bank of the Prosna, once surrounded by marshes and river backwaters. The site lies in Bolesławiec in Łódź Voivodeship, Wieruszów County, roughly 1 km from the village of Kolonia Bolesławiec-Chróścin, where the earlier stronghold stood. The ground on the mound is uneven, so sturdy shoes help.

The castle was besieged in 1391 or 1393 by Władysław Jagiełło's troops, who brought a bombard from Kraków but failed to take it; the smaller northern residential building was destroyed and never rebuilt. A clock in the tower window is recorded in 1541.