Isn't it strange how things like that fade out of public consciousness after only a few decades? I would have thought it would be nigh on impossible to hide/forget the existance of that much concrete, even in a city!
A few years ago here in Fremantle, a developer brought in the big earthmovers to create a light industrial/ shopping precinct on the edge of the Fremantle suburbs. Checked with the local council, pored over maps, records, etc, then promptly brought one of his massive blade machines to a dead halt (broke the blade......) against a concrete gun emplacement that had been there to guard the harbour since WW2. There were 3 of them, bloody huge, around 6m high and about 20m in diameter. Over the years the scrub and bush had grown over it, and everyone simply FORGOT they were there !?!?!?!