The square Slovenski trg in the centre of Ptuj is the scene of an open air lapidary collection, the oldest in Slovenia. The collection consists of pieces of civil and military tombstones, urns, sacrificial altars, relief votive slabs and ashlars. The northern wall of the tower contains, among others, the military tombstone of Gaius Rufius, a soldier of the Legio XIII Gemina, and that of Gaius Cornelius Verus, a veteran of the Legio II Adiutrix. Six memorials were built into the southern wall of the tower. Among them are a sacrificial altar, dedicated to Jupiter and decorated at the top with a Norican-Pannonian volute, and the tombstone of Marcus Ulpius Cutius and his family. The lapidary features also the Orpheus Monument, the largest tombstone ever found in the Roman province of Upper Pannonia.