[1] During the Medieval period, the temple was converted to a Christian church dedicated to Santa Maria Egyziaca ("St Mary of Egypt").

During Antiquity the site overlooked the Tiberine port at a sharp bend in the river; from here, Portunus watched over cattle barges as they entered the city from Ostia.

[3] The rectangular building consists of a tetrastyle portico and cella, raised on a high podium reached by a flight of steps, which it retains.

The Ionic capitals are of the original form, different in the frontal and side views, except in the volutes at the corners, which project at 45°, a common Roman detail.

The temple owes its state of preservation to its being converted for use as a church in 872 and rededicated to Santa Maria Egiziaca (Saint Mary of Egypt).