Frias castle 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.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.