There are many, many old photographs of the Arch of Constantine, the Colosseum, and the now-vanished Meta Sudans, the fountain that stood outside it and was demolished by Mussolini. A few more have come my way this week. For most of them I am indebted to the amazing Roma Ieri Oggi site and its twitter feed @romaierioggi.
The first is from 1930, and shows an unusual view:
(I do wish he would not vandalise the photo with a watermark).
Helpfully he has zoomed in on the Meta Sudans:
Another item is from some amazing aerial photographs from ca 1926 by Walter Mittelholzer. These may be found here. This one shows the area that we are interested in, although sadly the Meta Sudans is but a bump:
Another photograph via @PhotoVintageFr depicts the Meta Sudans from the opposite side:
While this one shows it peeking through the Arch of Constantine:
Finally there is this one, from here. It’s from 1850, and taken from high up in the Colosseum:
Really somebody ought to make a 3-D model of the structure as it was at this time!