Olyka Castle

Olyka Castle was the principal seat of the Radziwill princely family in Volhynia from 1564 until the late 18th century. The founder of the castle was Prince Mikołaj "the Black" Radziwiłł who gave Olyka to his youngest son Stanisław. Two senior branches of the Radziwill family were based in Nesvizh and Kletsk.

The Olyka Castle was immensely influential as the first square fort with corner bastions in the Kresy and the prototype of many similar structures found in Eastern Europe. It was almost continuously under construction for eight decades and sustained numerous sieges between 1591 and 1648. It is probably the biggest aristocratic residence in Ukraine, with 365 rooms.