In most of the Mithraea there was a portico which led into a second sacristy, where the ritual dresses were probably kept.
The Mithraea were spread all over the Roman empire and some 50 of these caves still exist in Rome today.
In the Aventine Mithraeum the followers of the god were shown in procession offering their gifts.
Three Mithraea have been excavated, at London, Carrawburgh, and Housesteads (Northumberland).
The widespread popularity of the cult is evident from the records of Mithraea which have been identified all over the empire, and which are still coming to light.