Funny, when I think about cities built on cities I think of Europe not the US.
This is facinating.
Next time you’re in NYC, go downtown to Pearl Street and see the foundation of the Dutch Stadt Huys (State House) built in the 17th Century. It is preserved under glass near a skyscraper down there...
Actually, a lot of American cities were built like that. You get a lot of building on top of older levels in cities on coastlines, due to the faster deterioration and the fact that the buildings sink so much faster. Reference Savannah, here in my home state, for some good finds. A great many of the older, historically significant buildings (The Pirate’s House, great example) have had to have structural work done to keep them from sinking any further. infact, it was during such work that the “Pirate Tunnel” beneath the Pirate’s house was unearthed, if i remember correctly.