The Temple of Portunus, with its rectangular ground plan, represents an important trace of ancient Roman architecture, the structures of which are almost intact. Such construction does not conform to the rules of Greek art. It would seem to date back to the 4th or 3rd century BC, although it appears to have been restructured after 70 BC.
The temple was located in a picturesque setting, which included both the temple devoted to Hercules and the nearby temple complexes of Mater Natura and San Nicola in Carcere. In the 9th century, the structures of the Temple of Portunus were altered to turn it into a Christian church, however, it has retained its external appearance intact. First called Santa Maria "Secundicerii" and later Santa Maria Egiziaca, patron saint of prostitutes, this church has been renovated several times over the centuries. In order to restore the ancient appearance of the temple, it was decided to remove the church in 1916. During the restoration work, a series of frescoes from the late Middle Ages was discovered, which was considered unique and is now more readable and eye-catching thanks to a recent restoration.