Monfalcone Castle, locally known as Rocca di Monfalcone or Castello di Monfalcone, lies on a mountain north of the town with the same name, north-west of the city of Trieste in the Friuli-Venezia Giulia region in Italy.
Originally a prehistoric fortified village, the site was occupied by a Roman observation tower, guarding the road from the town of Aquileia to Tergeste (Trieste), and later by a fortress dating back to the reign of Teodoricus.
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. For this reason it was known as "Friuli's watchful eye".
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.
It is supposed to be occupied by a paleontology museum of the surrounding Karst region. However when I visited the castle was closed, presumably for restorations. But it looked like it had been closed for a very long time. The castle can not be reached by car as far as I know. Nice castle, too bad it was closed.