That stands for Unidentified Roof Object.
Anyone want to take a guess.?
It will be good as mine.
Why, that is a solar water heater, Bob. See, it is painted black. 
…no idea.
Smart a-s- in every crowd.
A Chicago Still.
Looks like what left of an old heat exchanger for a water tower heater??
The tank is most likely a condensate return tank from the boiler. Here in Ga. it is uncommon that boilers are used for heat but I have seen this in industrial application’s
Expansion tank for the heating system. Open type.
Ok two thoughts but I like Kens best.
Haha that was my first thought.
Interesting that all 3 ideas are different but plausible.
Did not note tower stubs though Jeff and it is close to the edge of the roof though not near where the boiler would be below or in line.
Chimney was at least 30 feet from there
I like Michaels idea.
Yep. Old gravity hot water system. The building’s original system was circulating hot water, I’ll bet.
Here is the new one.
and for heat
