Bringing down a multi-story building in Manhattan, one of the most densely built up and heavily populated cities in the world is difficult but achieveable. Otherwise the constant re-building that occurrs in NYC would not be possible.
To bring a tall skyscraper down is a kind of de-building process, the exact opposite of what happened when the building was originally erected. Explosives can’t be used. Shots of what happens when buildings in NYC are subject to explosions for whatever reason illustrate why. The sudden eruption of building materials in such a confined space with so many people around does a lot of damage.
So the very first step is that the whole building has to enveloped in safety netting and scaffolding, see the first video which is pretty amazing. Then all the equipment and furnishings are removed and all the salvageable items such as copper wiring are also taken out. Finally all the acoustic ceiling tiles and other building elements are also taken out so only the structural elements that hold the building up, remain.
Finally the building is cut up starting at the top. One floor at a time it is all cut up and carted out until nothing remains. It is a very expensive process so many building are altered rather than being completely demolished, but there are still a number which are taken apart in the manner just described. In the second video, demolition prep is taking place so that the de-building process can begin. Thank you to the wonderful site Qhora from which I got my knowledge and also acknowledging tokyocheesesteak , a great videographer who, among other things, appears to be documentaing a large number of Manhattan buildings being demolished.