Workman digging in a field near Dormagen (Durnomagus) found a vault in which there was a chamber ten feet high, ten feet board and forty week long. Peter Delhoven, a prominent collector of Roman artifacts, particpated in the excavation of the mithräum. The interior walls still had evident traces of green and red paint on the walls.
Against one of the walls were found two monuments. The first monument was 2 1/2 feet high and two feet wide. It was made of limestone. Mithras and the bull depicted on the relief were damaged. The heads, arms and legs were damaged, but the loose garment of Mithras was of excellent workmanship. The tail of the bull terminated in three heads of wheat. Both the scorpion and snake were present with the latter coiling around a jar. There are other figures which appear on the tauroctony including a dog leaping up at the bull's wounds, there are also faces of Sol and Luna.
At the base is an inscription, D(eo) S(oli) i(nvicto) imp(erio) C Amandinius Verus buc(inator) v(otum) s(olvit) l(ibens) l(aetus) m(erito).
The second monument is also of the bull-slaying by Mithras. It is of white limestone, and is 2 feet high and 1 3/4 feet wide. The body of the bull is not complete with its head and much of its body and rear quarter missing. The bull's tail ends in three heads of wheat. Mithras' head, arms and legs are missing. The scorpion is in its usual place. There is also a crater and the snake. Cautopates is depicted cross-legged and holding his torch down. Cautes is also depicted with his legs crossed and his torch pointing up.
There is an inscription: Deo Soli i(nvicto) M(ithrae) p(ro) s(alute) i(mperatoris) Suran l(ibertus) dupl(icarius) ale Noricorum ci(vis) Trax v(otum) s(olvit) l(ibens) m(erito).
There were also found in the mithräum fragments of another monument, eight terracotta and one bronze lamp, and twelve round balls of tuffa stone. All of the finds are located in the Rheinisches Landesmuseum in Bonn.
The monuments of the bull slaying have placed an important part in the emergence of modern theories that Mithraism is a religion based on astrology and that the scene depicted on the tauroctony is actually a star map. Karl B. Stark first advanced this theory in 1869, and David Ulansey argues that the bull-slaying scene is based on the precession of the equinoxes through the zodiac.
Dorow, Wilhelm. "Alterhumer am Rhein," Kunst-Blatt, zweiter Jahrgang 1821. Stuttgart und Tubingen, pp. 358-360
Fiedler, F. "Durnomagus oder Dormagen und dessen Denkmaler der Romerzeit," `Jahrbucher des Vereins von Alterthumsfreunden im Rheinlande. Vol 31 (1854) pp 45-56.
Stark, Karl B. "Die Mithrassteine von Dormagen." Jahrbucher des Vereins von Altertumsfreunden im Rheinlande. Vol. 46 (1869) pp 1-25.
Ulansey, David. The Origins of the Mithraic Mysteries. New York: Oxford University Press, 1989
Deo Soli i(nvicto) M(ithrae) p(ro) s(alute) i(mperatoris) Suran l(ibertus) dupl(icarius) ale Noricorum ci(vis) Trax v(otum) s(olvit) l(ibens) m(erito)