It's the famous pyramid of Caius Cestius, an enderaing view for me, who used to wait for the bus bringing me to high school over there, and a mysterious, intriguing building from whoever happens to walk by.
Always according to the inscriptions, we got to know that "The work was completed, in accordance with the will, in 330 days, by the decision of the heir Pontus Mela, son of Publius of the Claudia, and Pothus, freedman", in fact the completion of the funerary monument within 330 days was the condition for the relatives to inherit his fortunes.
From this testament it was possible to date the construction of the pyramid within a determined period and to get to know more about Caius himself.
For example, we got to know that he used to collect precious fabrics from all around the (known!) world, and that he asked his heirs to place his favourite pieces of Attalic tapestries (embroidered in gold, they became popular among the higher classes once Attalus II bequeated his Kingdom to Rome, sending there clothes and tapestries decorated in such way). Unfortunately, though, due to a law of the 12 AC that prohibited the waste of luxuries for tombs, the heirs of Caius had to sell the tapestries and made two bronze statues with the money, statues that would be lost during the years.
The interesting thing about this matter is that the company of the honorable Yagi-san, the mecenate who donated to restore the marble cover of the monument, trades with the export of texile products for international fashion brands-- Many of us wondered about the incredible coincidence.
To spare materials for the construction, he decided to include in the walls some monuments that would act as part of the fortification: the Pyramid of Cestius is one of them. It guarded the Porta Ostiensis, still recognizable today in the Porta San Paolo, and was served by a little gate, the posterula, used for pedestrian traffic, still visible.
The pyramid of Caius was not the only one to decorate the Capital back then.
As the apex of the Roman "Egyptmania" dates 31 BC, with the defeat of Cleopatra and Antonio by the hands of Ottaviano in the battle of Athium and the resulting importation of obelisks and other cultural treasures from Egypt, but it must be noted that the passion for Egypt and its exotic culture started during the reign of Caesar, with the visit of Cleopatra in Rome on 46 BC, even if the first temples dedicated to "romanified" Egyptian deities (like Isis and Serapis) made their first appearances even earlier.
There are mentions about other pyramids being built in Rome, the most famous being the one located by Castel Sant'Angelo, considered the "twin" of Cestius' and being portrayed in various masterpieces (here you can spot it in the background together with Castel Sant'Angelo and its bridge in the rendition of "The Vision of Constantine" by a student of Raphael) before its destruction for the Jubilee of 1500 by Pope Alexander VI Borgia, for the making of the "Via Recta" (or "Alexandrine Street"), a straight road starting from Sant'Angelo bridge to Saint Peter's, an attempt to simplify the pilgrimage (and the very first ancestor of the debated Via della Conciliazione).
"Meta Remi" was the name according which the Pyramid was known during the Middle Ages, and it's kinda weird, as the name of the owner was still quite visible, so it's thought that it was just an attempt of the locals to give more appeal to the sites, as tourists were already active back then.
Grave robbers, thinking that it was similar to Egypitian pyramids in its contents, entered the place and destroyed pretty much the original decorations and walls of the dead chamber. Because of this first sack, we don't know if it contained a sarcophagus or a simple urn.
When we entered the place we got to see the destruction caused by the grave robbers that were searching for treasures and most importantly the hole from where they got in, as the tunnel was preserved in its integrity, even if its entry was obviously closed.
They show references to the religious activities of Caius: the depiction of chandeliers, the little figures of female priests with instruments, all of them are connected to the ministrations of epolunes.
The place was made without any entrance and it was closed once the remains of Caius were placed in there.
The entrance from where we got in was the making of Pope Alexander VII Chigi, who promoted the first restoration works on the Pyramid. As it was a popular hit with pilgrims and part of the "Mirabilia Urbis" of the times he excavated the site, cleaned up the walls and remains around, put back in place the columns and made a proper entrance to the site. For a time he even considered the idea to turn it into a chapel, but fortunately he changed his mind.
Speaking of pilgrims, you can still see the signatures of those guys on the walls of the chamber: