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 (1515–1565) who gave Olyka to his youngest son Stanisław. Two senior branches of the Radziwill family were based in Nesvizh and Kletsk. Other buildings of the castle complex include a 17th-century gateway, a two-storey clock tower, and the Collegiate Church of the Holy Trinity (1635–1640), an elaborate replica of Il Gesu.