Based on information from medieval written sources and archaeological research in 1989, it is reasonable to believe that the castle served as a defensive residence for magnates. ‘Castrum Bydlin’ and ‘fortalicium Załęże’ appears in numerous references from 1389 onwards. The castle was probably built by the knight Niemierza of the Strzała coat of arms or his father, Pełka. At the end of the 15th century Bydlin became the property of the Brzezicki family, followed by the Szczepanowskis and the Boners.

In the second half of the 16th century, Jan Firlej converted the knight's castle in Bydlin into an Arian church. At the end of the 16th century, the next heir to the village, Mikołaj Firlej, governor of Kraków, rebuilt the former fortified residence and changed the church into a Catholic church dedicated to the Holy Cross. The reconstruction consisted of erecting a rainbow wall in the middle of the rectangular interior, which separated the chancel from the nave. A narrow porch interior was partitioned off to the west, a new entrance was broken at the courtyard level, and windows were bricked up. The church was burned down during the Swedish Deluge in the 17th century.

Only the ruins of the castle have survived to the present day – the remains of the walls and the moat – which are part of the Trail of the Eagles' Nests. The average thickness of the walls of the Bydlin Castle was just over two metresin contrast to the average height, whichis around seven metres. The walls show traces of built-up gun windows. The castle ruins are available to visit for free.

Traces of World War I trenches from the battles in November 1914 have remained at the foot of these ruins. At the beginning of the First World War, on 17–18 November 1914, near Bydlin and Krzywopłoty, some 1,400 soldiers of the 6th Battalion of Józef Piłsudski's 1st Polish Legion Brigade, together with Austro-Hungarian troops, fought a tough but victorious battle with Russian troops. Forty-six Legionnaires died and were buried alongside the others of the fallen in the local cemetery. At the entrance to the historic cemetery, one’s attention is drawn to the 18th-century stone chapel of the Consolation of the Blessed Virgin Mary, which was originally a hermitage.

The village of Bydlin lies about 10 kilometres from Olkusz, and the red Trail of the Eagles' Nests and the red Bicycle Trail of the Eagles' Nests lead to the castle.