Castillo de Aguas Mansas in Agoncillo, La Rioja, is a medieval fortress in exceptional conservation condition, its name translating to 'Calm Waters' or 'Quiet Waters.' Built during the 13th and 14th centuries, the castle underwent substantial remodeling in the 14th century by Rodrigo Alfonso de Medrano, who invested significant resources in expanding and updating the fortification. The rectangular structure is flanked by four towers with machicolation, while a Calatrava Cross emblem adorns the entrance. Today the castle serves as the municipal seat and houses the town library, with a permanent exhibition on La Rioja's castles and fortresses. Visitors can walk the grounds to observe the moat and defensive walls surrounding the keep and parade ground.
