Porta Santo Spirito

Roma Capitale's tourism office states that the gate stands on what was the southern limit of the Civitas Leonina, walled by Leo IV around 850, and that Sangallo rebuilt it for Paul III after the Landsknechte of Charles V sacked Rome in 1527. Bastions were added around it by Pius IV in 1564. It has a large central archway flanked by pairs of Doric columns and niches. In 1642, under Urban VIII, the building of the Mura Gianicolensi enclosed the gate inside a new circuit and it lost its function. Italian Wikipedia adds the earlier name posterula Saxonum and a renaming under Innocent III. This is also the Roma Capitale page that gets the 1527 Sack right, against its own Castel Sant'Angelo page.