The Porta Romana or Roman Gate belongs to the city walls of the first century BC. Visitors from Rome followed the Via Ostiensis and entered Ostia through this gate. It was excavated in 1911. The gate was at a much lower level than the present level. In the interior two rooms were created by large tufa blocks. Grooves for wooden doors were found on the east side (the outer side). On either side of the gate is a square tower, with sides of six metres.

Large inscriptions, high up on either side of the gate, recorded the building history of the gate and the city wall. The inscriptions have now been attached on a nearby wall. The city wall was built in the first century BC by Marcus Tullius Cicero, and finished by his rival Publius Clodius (for details see the topic The city walls). The inscription also records a restoration of the gate during the reign of Domitianus (81-96 AD): the level was raised, the gate was rebuilt, and marble architectural decoration was added. The remains of the decoration have been attached to the north side of the gate.

A huge statue of the winged Minerva-Victoria, found on the nearby Square of the Victoria, stood on top of the gate. Minerva was the favourite goddess of Domitianus. The find of the statue caused quite a sensation at the beginning of the 20th century: it was depicted often and praised by visitors. The original is now in the museum, a copy can be seen near the gate, standing in isolation.

To the north-east of the gate is the so-called Cippus of Salus Augusti. It was found in 1910. It is a marble base for a statue (1.20 x 1.20 x 1.05), with the inscription:

A statue was set up for the well-being (salus) of the Emperor, on top of the base. It has been suggested that it was a statue of Salus Augusti, a woman with a snake, but it could well have been of another deity: dedications to various deities for the health of the Emperor are common. A certain Glabrio took care of the dedication, by decree of the decuriones, the local city council. Glabrio was a member of a well-known Ostian family, the Acilii Glabriones. Modern Acilia, to the north of Ostia, was named after this family by Dante Vaglieri, one of the excavators. Glabrio was patron of the colony. The base is at the lower level, and was installed in the first half of the first century AD, presumably when an Emperor visited Ostia and entered the city through this gate. Here we may think of Claudius, who was a frequent visitor of Ostia when the harbour at Portus was built.

In 1858 a marble sun-dial was found near the gate.