The Castillo fortaleza de San Vicente de la Sonsierra is an impressive medieval castle that rises above the River Ebro. It was built in the 12th century by the Kingdom of Navarre to defend its border with Castile. It was part of a defense line connecting Laguardia and Labastida, and was the largest fortress in Navarre on the Ebro. The castle has a semi-circular shape that adapts to the rock on which it stands. It consists of three walled areas: the albacar, where the houses of the old town stood, the cortijo, where the parish church, the chapel of San Juan and the cemetery are, and the castle itself, with the keep and the bell tower. The castle lost its military importance after the annexation of Navarre by Castile in 1512, and was later used as a quarry and rubbish dump. In the 20th century, people began to realize its historical and artistic value, and several restoration projects were carried out. The castle is now a monument of cultural interest and a tourist attraction