Ptuj was an important place in Roman times, so it's not surprising that there are various remains still visible.
The ancient religion of Mithraism probably originated in Persia, and spread across the Roman Empire. It was very popular with the army, and was very male-dominated. Not much is known about the rituals or practices, but there were certainly initiation rites involved, and various rankings of believers.
There are four Mithraic shrines in Ptuj, but the main one is on the Maribor road (Mithras lll). Discovered in the early 20th century, it's housed in a purpose-built building and contains both the remains of the shrine itself and various sacrificial altars and carved stones from this and other shrines. Worth making the effort to visit.
Take the road to Maribor (Mariborska Cesta) and watch out for the signpost on your left. You'll have to get the key from a house nearby (there's a notice on the door; I think it's number 3).
................because I can't remember what road it was on. Towards the river though, and on the corner of two streets. I thought he was lovely, and wondered why he was there. Animals such as elephants were sculpted onto pharmacists' premises in Medieval Krakow, so maybe he is something to do with that.........or maybe he's just for good luck?
Anyway, he's worth looking out for.
Please look for local festivities - they are great!
It is the right moment to learn about the culture of Slovenia. The village will be dansing and drinking together and you will be invited to do also.