Castell de Montoliu, also known as Castell de Santa Margarida or el Castellot, stands in the eastern Tarragona plain near the Gaià River mouth, with its earliest documented mention appearing in 1118. The castle passed through noble families including the Claramunt and later the viscounts of Cardona, maintaining strategic importance throughout the medieval period. Well-preserved structures include an 11th-12th century circular tower and a rectangular body with pointed vault from the 13th-14th centuries, set within a roughly rectangular walled perimeter measuring approximately 30 by 15 meters.
