Now housing the Museum of the Samnium, Rocca dei Rettori fortress has origins dating back to prehistoric times, with a Samnite necropolis (7th-6th century BC) and Roman baths later built on-site. The Lombards fortified the area, adding the Big Tower (Torrione), and an 8th-century Benedictine monastery was later merged into a castle under Duke Arechis II. By 1321, Pope John XXII restored it as a papal residence, and in 1586, it became a prison until 1865.
Perched on Benevento’s highest point, the Rocca consists of two main structures. The Big Tower (Torrione) is a 28-meter Lombard-built tower, modified over centuries, featuring Roman wall fragments, ogival double windows, and turrets. The Palazzo dei Governatori Pontifici is a three-floor palace with barbicans, framed windows, a colonnade, and 18th-century wooden ceilings. The lowest floor housed prison cells, while the upper halls boast elaborate decorations.
The rear garden contains Roman ruins, including slabs from the Via Traiana. A 1640 Lion Monument honoring Pope Urban VIII stands at the entrance, featuring a medieval lion atop an octagonal Roman pedestal.
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.