In the period of Roman domination, the inhabitants of Singidunum practiced oriental and syncretistic cults, dedicated to Mithras, Nemesis, Kybele, Hecate, Orcus, the Thracian Horseman, in addition to the official ones. The old, local beliefs of the autochthonous population were also retained.
A number of lead plates of various type, as well as marble icons illustrating scenes from the mystic cult of the Danubian horseman, have been found in the town itself and in its broader area. A rectangular lead plate, with scenes arranged in two zones, is a unique and remarkable find in every respect. The upper zone represents the celestial world, with the busts of Sol and Luna, flanked with heraldic snakes. The central place in this zone is occupied by the figure of an unknown goddess between two horsemen. A particularly interesting feature in the second zone is the central figure of a nude man, whose posture, and the whip behind his back, are identical with those of the Sol on the reverse of the coins minted from the time of Emperor Gordian III on.
This find may prove of exceptional importance for the future study of this little known mystical cult, named "Danubian" because a number of such small icons have been found along the limes on the Danube in Lower Pannonia, Upper Moesia and Dacia. The autochthonous element is no doubt dominant here, but its origin it not clear. The influence of oriental religions, particularly Mithraism, is also very prominent in the cult.