Early in date, and closer to the Tiber than the nearby Theatre of Marcellus, are two small temples of unknown identity, built in the low-lying district by the river which was the ancient cattle market, or Forum Boarium. Heavy traffic thunders past them along the river's bank, but plots of grass and flowers enclose the ancient temples of timeblackened stone, while a medieval church and a baroque fountain add their note of continuity and change.
The rectangular temple, only a corner of which is visible in either photograph or drawing, was built of native tufa and travertine in the days of the Republic, before Augustus had made common the use of marble. Long called the 'Temple of Fortuna Virilis', and sometimes that of 'Mater Matuta', it has been thought lately that it may have been a temple to Portunus, guardian of this section which was the Tiber port. Actually, however, its name is still unknown. It owes its excellent preservation to the fact that it was converted in the ninth century into the church of Santa Maria Egiziaca, Saint Mary the Egyptian. It was restored to its ancient condition in the twenties of this century.
The true name of the round temple is equally lost in mystery, though, because of its shape, it has long been commonly but mistakenly called the 'Temple of Vesta'. Its marble columns and walls belong to the time of Augustus, though its foundations may be earlier. Originally it had the entablature proper to its Corinthian columns, but this disappeared some time in the Middle Ages and was replaced by the present conical roof. This temple too owes its preservation to its use as a church. In the twelfth century it was known as Round Saint Stephen's. The Mirabilia explains that 'the Round Saint Stephen's was the temple of Faunus' and identifies Faunus as 'the idol that spake to Julian and beguiled him'. This 'idol', according to legend, was a pagan image, said by some to be Mercury, which spoke to Julian the Apostate, Constantine's nephew, and tempted him to the pagan faith. In the sixteenth century the church was called Santo Stefano delle Carrozze, from the wagon-shops nearby; still later, about 1700, it was renamed Santa Maria del Sole, Saint Mary of the Sun.