Fuentidueña de Tajo Castle is a large, irregular building standing on a hill which dominates the Town and the Tagus River. It is believed to have been built during the 12th century and has been extended and rebuilt later on in the 14th century. It is related to the Kings, Alfonso VI and Alfonso VIII.
It still has a wall and part of the cylindrical towers on the sides. The two sections composing it are separated by an interior moat. It is still possible to see the Homage Tower opposite the Town.This castle was the Headquarters of the Kingdom in the time of Da Urraca, wife of Alfonso I the Warrior; legend has it that at night she used to walk through the hidden corridors to visit the Moors.
The provincial Governor, Pedro Manrique, was imprisoned in this Castle by order of Juan II. Álvaro de Luna, Marquis of Villena, was also made prisoner for his discrepancies with the Order of Santiago; he later became the proprietor of the Castle.
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.