Looks like it was part of a larger set of renderings called "Italia Vostra: Restoration of Historical Centres".

Referenced in this Artforum article:
http://findarticles.com/p/articles/mi_m0268/is_7_42/ai_n6005388/pg_2/

You might have already have found this, though....

(belated) thanks, gresham. 

I did manage to find a reference in this Superstudio bibliography... 

I'm betting this is the same project(s):

‘Salvaging the historical centres of Italy’ / article by Superstudio
in   Argomenti e Immagini di Design  no.5  May/June 1972 / p.4-13 
 

now if only I could find a scan or a reprint....

Is it a photomontage - aerial black and white of the Colosseum or with a line/halftone drawing of a donut-like apartment building stuck on top?  If so, it's in <I>Superstudio: Life Without Objects</i> (Milan: Skira Editore/New York: Rizzoli, 2003), spanning between pages 134 and 135.  No caption or other info provided.  Can scan if you need it, but there'll be a big SPINE running down the middle.

The "rescue of historic centers" series seems to be in a rather different style, the photomontages of Florence flooded up to the level of the Duomo, etc...but perhaps the line drawing was related somehow...

huh, note to self, don't try to use HTML on archinect...

codename-albacore (if that is your real name...) -  thanks. The one I'm thinking of is the line drawing of the apartment block atop the Colosseum (and any drawings from the same series?)

does the text in "Life Without Objects" offer any context? Original publication dates? 

I did manage to find a few of the (great!) photomontages on flickr:

Check your email.  Like I said, no captions or other info.  Flipped through some other Superstudio stuff in the library with no more luck.  Very mysterious.