A while ago there was a story about one Moscow city street advertisement agency.
What made them famous? Their attempt to install a new street ad stand, so they had to hammer in a concrete pile into ground. They started doing this and suddenly the pile came down through ground layer and disappeared somewhere down there.
Yes, they were shocked but they had a task to accomplish so they started to smash in another pile – it also broke in through the ground. Now they got really puzzled.
So where have their piles gone? They gone right into a subway train, nailed a full of people subway train moving at 40mph (70kmh) down to the ground – right in the middle of the working day. They got extremely lucky that the subway car in which they hammered in a pile was almost empty and nobody got seriously injured.
This is how the metro car looked after the incindent.