Klein Bijgaarden is a neoclassical castle in Sint-Pieters-Leeuw, Belgium, with origins dating to approximately 1250 as a Bernardine convent where nuns drained marshlands to create productive farmland. In 1800, Guillaume Wittouck purchased the former monastic buildings along with 100 hectares of land. Major renovations by his descendant Félix-Guillaume in 1866 transformed the old cloister into the distinctive neoclassical castle seen today, designed by architect Beyaert. Features include a U-shaped brick structure with arduin stone details, rounded arch windows, an ornate Corinthian portal, and decorative roof dormers. The Wittouck family served as burgomasters for three generations. Currently operated as a retirement home, the castle represents centuries of Belgian architectural and social history.