Only a few weeks before I left Rome, I acquired a Rapidograph technical drawing pen and loaded it with a reddish-brown ink made by Pelikan of Germany. The pen was the metric equivalent of a 4 - 0 very thin point but it made a great line in architectural drawings. I drew every day with this pen, including ordinary Roman scenes like this building, which was next door to my temporary residence. The building here is the "Ospizio Don Orione", a small home for the elderly. From its Website (in Italian) it sounds like a peaceful place to, uh, finish up. The walls are painted that characteristic bright orange of Roman stucco.
I used that technical pen in the USA too but found it too difficult to maintain. The Rapidographs, as any artist/designer who used them will tell you, tend to dry up, clog, or leak. The introduction of the disposable and highly efficient Faber-Castell "Pitt" technical drawing pens in sepia or black solved the problem and that is the drawing pen I still use today, 40 years later.
"Ospizio Don Orione" is brown tech pen ink on thick paper, colored in watercolor and watercolor pencil, 9 1/2" x 7", 1976. Click for a larger view and a peaceful old age.