A painting in an alcove, protected from the rain by a wooden overhang. I don't remember exactly where this was. Rome is full of strange little places like this, not even marked on the map. There will be a bit of aquaduct here, a bit of column there... and paintings that predate the Declaration of Independance simply whiling away the centuries in an alley.
But Rome is full of signs of history. Here columns have been repurposed to help build the wall of this church. Later, we decided to take a look inside this church, as we had the Marias. We happened into a free tour of the church's basement. The church was built about 800 years ago, on the site of a Roman temple to Saturn. Two other temples were on either side of it, and when the church was built it encompassed the ruined walls of these other two temples, which is where the visible colunns came from. Saturn was also the god of wealth, and so the money was kept in the basement of the temple. Fear of divine retribution alone was not enough to guard the money, though, and in the basement you can see grooves on the floor where a heavy stone door was slid to close the vault. In another area, there is evidence that the vault was used as an occasional ossuary - a few human bones remain in an alcove. One layer of stone deeper, there remain flat paving stones from the 7th Century BC, where the site was part of a marketplace before the Roman temples were built. It was far too dark to take photos in the clammy basement of the church, but it was one of the best tours I've taken... and that in a church unmarked on Rome's maps.
This little bit of wall and archways is along the Via del Teatro Marcello, and if I remember correctly it is almost immediately across the road from the ruins of the famous theater. However, I am unable to find any mention of it in any of the Rome tour guides, maps, etc. that I've been consulting. No one else seems to care about a couple of arches, built of heavy stone in the style of the 1st century BC, and repaired with bricks typical of the 1st-3rd centuries AD. Given the cars visible in the lower right of the photo, I would guess that the Via di Monte Caprino runs behind it... but it might be on the next corner down, along the North edge of the Piazza della Bocca della Verita, as I remember this wall being not too far from the Circus Maximus. If anyone knows what it is, please feel free to tell me.