Torre di Montesarchio, Medieval tower in Montesarchio, Italy.

Torre di Montesarchio consists of two cylindrical bodies: a taller, narrower inner core and a lower, thicker outer ring, plus a side block to the south and an almond-shaped block protecting the entrance to the east. The inner cylinder is built more roughly, with less worked stone and added bricks. The tower now houses the Museo Archeologico Nazionale del Sannio Caudino together with the castle.

The tower's present form stems largely from a design by Sienese artist Francesco di Giorgio Martini, who inspected castles across the Kingdom of Naples in 1495 and adapted the structure to cannon warfare with round, low, thick walls. In the 19th century it became a political prison; Carlo Poerio, an opponent of the Bourbon king, was held in a cell now open to visitors. The inner cylinder, built with rougher stones and bricks, may date to a Lombard fortification licensed after 938, when the princes of Benevento granted Caudi to the gastald Teoderico, called Mirando.

The tower and castle now house the Museo Archeologico Nazionale del Sannio Caudino. Volunteers of the Sentinelle della Torre association open the tower in agreement with the municipality and the Superintendence, and guided tours lead visitors into the cell where the Bourbon opponent Carlo Poerio was held.

The easiest way to reach the tower is by following marked pathways from the town center of Montesarchio to viewing areas around the structure. Wear sturdy shoes since the climb to the hilltop involves uneven terrain and some steep sections.

Excavations around the tower uncovered artifacts showing that people lived in the area long before medieval times. These archaeological finds reveal how much deeper the area's history runs than just the visible tower.