[1] Its current designation as the Arch of Portugal is derived from its location where it stood against the Palazzo Fiano, where from 1488 to 1508 lived the Portuguese cardinal Jorge da Costa, Cardinal Priest of the church of San Lorenzo in Lucina.

For many years it was believed that the arch formed part of an aqueduct branch, with most suggestions linking it to the Aqua Virgo.

However, most modern studies now attribute the arch to the period of late antiquity, possibly during the reign of Aurelian (r. 270–275), hypothesising that it acted as a monumental entry into his enormous Temple of the Sun.

Uncovered at a separate location from the others, but most likely related, the adventus of Hadrian shows the emperor welcomed by three personifications, representing the goddess Roma, the Roman Senate, and the people of Rome.

The three Hadrianic reliefs were placed at around the same time in the staircase of the Palazzo dei Conservatori (today the Capitoline Museums).