The existence of a mithraeum in the "tana del lupo", a natural cave in the castle of Angera, has been assumed since the 19th century, following the discovery of two mithraic inscriptions in the town.
This high stele by a certain Acilius Pisonianus bears an inscription commemorating the restoration of a Mithraeum in Mediolanum, today's Milan.
TNMM650 – CIMRM 706
D(eo) S(oli) i(nvicto) M(ithrae) / P(ublius) Acil(ius) Piso/nianus pater / patratus qui / hoc speleum / vi{i} ignis ab/sumtum com/parata area a re-/publ(ica) Mediol(anensi) / pecunia sua / restituit.