Monfalcone Castle, locally known as Rocca di Monfalcone or Castello di Monfalcone, lies on a mountain north of the town with the same name. Originally a prehistoric fortified village, the site was occupied by a Roman observation tower, guarding the road from the town of Aquileia to Trieste, and later by a fortress dating back to the reign of Theoderic the Great (around 490 AD).
As a stronghold of the Patriarch of Aquileia, overseeing the County of Duino, the castle was long contended for by the Patriarch and the Count of Gorizia, but was also a 'free commune' holding a seat in the Friulian Parliament.
Having surrendered on 14 July 1420 to the troops of the Venetian doge, Tommaso Mocenigo, it became an important outpost for the protection of the Venetian mainland against the Count of Gorizia and the Austrian Emperor and a defence against the attacks of the Turks.
In 1797 it came under Austrian rule and on 9 June 1915 it was occupied by the Italian army.
The castle is a square keep surrounded by a circular wall and a low earthen wall.
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.