What it says on the tin, a Cooling Tower from the Heljan Power Plant set.
Works as a smaller 15mm for me, or as a decent 6mm one as well. Even though it is a crap Heljan kit (it's not prefectly round, it split at the seam twice while tacking it down to unwarp it and it actually flew across the parking lot when the wind caught it, it bounced a few times and then split at the seam again.....), I've looked it up again and found a few for sale. 40$ in the States, 45 euro local. Of the set I only really like the cooling tower, and that kind of money isn't worth it (if I had it)
Concrete is blue-grey foundation painted over with Dheneb Stone. Weathring with some pinwashes and diluted off white for detailing, and no base....It would be very akward to paint the insides otherwise.