From piazza Fiume, two short diversions can be made.

• For the first one, follow via Calabria; at the first crossing turn left, and walk along via Collina, to piazza Sallustio. Here, several metres below the present ground level, you can see a Roman hall with a very high vault. This site [map ref. g] was named Sallust's Gardens after Sallust, a tribune and historian who lived in the 1st century BC. In those times, this area lay outside the republican walls. i.e. the city's older boundary. The Roman obelisk which today stands at the top of the famous Spanish Steps was originally found here, as well as some important statues now housed in the Capitoline Museums (among which the famous dying Galatian).
  Unfortunately, the site is not open to the public, and can only be seen from the square.
  
  
• Back in piazza Fiume, the second diversion is along via Salaria: about 350 metres off the square, now surrounded by buildings, stands a tomb in the shape of a large cylindre [map ref. h], once completely covered with turf, where trees and other vegetation likely grew, according to the typical fashion of mausoleums (monumental tombs) that housed the ashes of high personalities.

The inscription on the front tells us the name of the dead, Lucilius Paetus and his sister Lucilia Polla. It dates back to the late 1st century BC, at the beginning of Rome's imperial period. As the previous site, also this one cannot be accessed by the public, and can be only seen from the street..

Back on the walls route, from piazza Fiume keep following the outer side, and very soon you will reach a large memorial with a tall column in front of it [map ref. i], in memory of the historical event that affected Rome's modern history in a most crucial way: the breach of Porta Pia was opened on this very spot. On September 20th, 1870, the Italian troops that besieged the only city left under the rule of the pope, succeeded in opening a passage through the wall; as the Bersaglieri corps rapidly took hold of the city, the centuries-old Papal State came to an end, and Rome finally turned under the jurisdiction of unified Italy, eventually becoming its capital city soon after.
The event is remarked by an inscription on the column, which ends with the touching words: "...through this breach Italy once again entered Rome".

Not much further, we reach a fourth gate, Porta Pia [map ref. 4]. Its crenellation and its Renaissance look similar to that of Porta del Popolo, clearly reveal that this is a much more recent structure than the Roman wall: pope Pius IV had it built in the mid 16th century; who drew its project was Michelangelo.

Up to those days, the ancient road called Nomentana (from the Latin name of the small town it reached, Nomentum, presently Mentana, see map of ROME'S ANCIENT SURROUNDINGS) ran behind this wall, more or less along the first stretch of the present via XX Settembre, and made a bend in order to pass through the nearby small Porta Nomentana [map ref. 5], an original Roman gate. Therefore, the aim of Porta Pia was basically to provide an easier and wider access to this main road.
In the late 1800s architect Valadier refurbished the gate, altering its original Renaissance look.
Still today this spot is a busy approach to the city center.

Due to the above-mentioned facts of 1870, the central part of the gate now houses a museum dedicated to these troops, and a monument in the middle of the square remembers the Bersaglieri corps.
Just inside the gate, on the left side of via XX Settembre, an interesting modern building (1971) by the English architect Basil Spencer houses the British Embassy.

Soon after, following the wall, we come to the above-mentioned Porta Nomentana [map ref. 5], a secondary gate; when Porta Pia was built, and the course of the old via Nomentana was moved towards it, this passage became totally unused, and was closed for the sake of the walls' security. It can still be told, by the base of the surviving semicircular tower, by the different brick texture of the wall.

Note how, unlike Porta Pinciana (and other major gates), Porta Nomentana had no white stone facing, or similar additional elements; all the Roman gates must have originally looked quite similar to this simple yet rather steady brick structure.
Behind the closed gate are the grounds of the aforesaid British Embassy.

As we carry on along the wide street, now called viale del Policlinico, a tower with windows marks the site where Aurelian's wall joined the Castrum Praetorium, described in part II.