It stands in piazza della Bocca della Verità, where the Forum Boarium once was, not far from the temple of Hercules and from the oldest harbour on the Tiber, and it is one of the few buildings of ancient Rome to have come down to us perfectly preserved. The reason is simple and a little paradoxical: in the ninth century the temple was turned into a Christian church, first under the name of Santa Maria Secundicerii and then as Santa Maria Egiziaca, patroness of repentant prostitutes. The church structure was fitted inside the building without touching its outside.
What to see
It is an Ionic and tetrastyle temple, that is with four columns across the front, on a pseudoperipteral plan: at the front, on the pronaos, the columns stand free; along the sides and at the back they become half-columns set against the wall of the cella, as though the colonnade ran all the way round but stayed caught in the wall. Look at the stone, because it is not all the same: the columns of the pronaos and those at the corners of the cella are of travertine, the others of Aniene tufa. The tufa parts were probably plastered, to give the eye the effect of marble.
Visiting
The building you see has been dated, from the material found in its foundations, to the years between 80 and 70 before Christ, but underneath there are traces of earlier phases. In the oldest, between the end of the fourth and the beginning of the third century before Christ, there was a long podium of Grottaoscura tufa, which during the third century was linked to the pons Aemilius by a small masonry bridge. The temple stood inside a sacred enclosure and was altered around the first half of the second century before Christ, when the ground was raised: perhaps because of work on the banks of the Tiber.
Our editors' tip
Look for what is left of the church. In 1916 the church structure was removed to bring the temple back to its ancient look, but inside the early medieval frescoes telling the story of the saint can still be seen. So the monument tells itself twice over: outside the republican temple, inside the paintings of the church that let it cross the centuries. The name has changed too: for centuries it was the temple of Fortuna Virilis, and only in the nineteen-twenties was it identified with the temple of the god Portunus, the one Marcus Terentius Varro recalls.