Slovenski trg in the centre of Ptuj is the scene of an open air lapidary collection, the oldest in Slovenia. This collection was named after curate Simon Povoden, who in 1830 determined that collected classical stone memorials should be built into the inner walls of the municipal tower. Among them are 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 XIII Gemina legion, and that of Gaius Cornelius Verus, a veteran of the II Adiutrix legion. 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.