Its origins date back to the 9th century, when Alfonso VIII repopulated the valley to reinforce the border between Castile and Navarre. The historic quarter preserves its medieval atmosphere, and urban layout.On the tallest, most rugged end of a hill, the castle of the Duke of Frías stands, with its beautiful and well-kept mullioned windows, and 13th-century Romanesque capitals. In the city centre we must point out the church of San Vicente, whose Romanesque main front was taken to New York after the tower fell in 1904, and the convent of Santa María de Vadillo, founded at the beginning of the 13th century. Near the town, crossing the Ebro river, we see a gorgeous medieval bridge, with a defence tower that dates from the 14th century.