Around 2012 I was working near 5th Ave and 14th st, and there was a giant water main break. They had to dig about three stories down in a large intersection, and you could walk near the edge and look in.

It was extraordinary, like something out of a sci-fi where an alien ship has been torn open and the mess of pipes and wires looks organic. It was also a funny case of lost tech / organizational memory -- I heard they had to ask the union to help find retired folks who had worked on the lower levels and could explain why pipes were laid out the way they were.