Some remains of many Roman temples survive, above all in Rome itself, but the relatively few near-complete examples were nearly all converted to Christian churches (and sometimes subsequently to mosques), usually a considerable time after the initial triumph of Christianity under Constantine. The decline of Roman religion was relatively slow, and the temples themselves were not appropriated by the government until a decree of the Emperor Honorius in 415. Some of the oldest surviving temples include the Temple of Hercules Victor (mid 2nd century BC) and Temple of Portunus (120–80 BC), both standing within the Forum Boarium. Original marble columns of the Temple of Janus in Rome's "Forum Holitorium", dedicated by Gaius Duilius after his naval victory at the Battle of Mylae in 260 BC, still stand as a component of the exterior wall of the Renaissance era church of San Nicola in Carcere.