The complex of the Osoppo fortress, restored after the earthquake of 1976, is a mighty set of defensive works, tunnels, ditches, entrenchments, casemates. It was an ancient Celtic settlement, and later became a Roman oppidum (stronghold).
After the year 1420, the fort became the focal point of the defense of the "land state" of the Serenissima. It was fiercely defended against the imperials by Gerolamo Savorgnan in the year 1514.
Occupied two times, then, by the French in 1797 and 1848 - during the struggles of the Risorgimento - the fort, held by a group of Italian volunteers, resisted for seven months against the Austrians who wanted to recapture it.
