The following italics is a cut and pasted from: science.howstuffworks.com/engineering/structural/building-implosion.htm
 
 "In this article, we'll find out how demolition crews plan and execute these spectacular implosions. The violent blasts and billowing dust clouds may look chaotic, but a building implosion is actually one of the most precisely planned, delicately balanced engineering feats you'll ever see.
 
 You can demolish a stone wall with a sledgehammer, and it's fairly easy to level a five-story building using excavators and wrecking balls. But when you need to bring down a massive structure, say a 20-story skyscraper, you have to haul out the big guns. Explosive demolition is the preferred method for safely and efficiently demolishing larger structures. When a building is surrounded by other buildings, it may be necessary to "implode" the building, that is, make it collapse down into its footprint.
 
 Sometimes, though, a building is surrounded by structures that must be preserved. In this case, the blasters proceed with a true implosion, demolishing the building so that it collapses straight down into its own footprint (the total area at the base of the building). This feat requires such skill that only a handful of demolition companies in the world will attempt it."
 
 Please note that according to present day science and technologies, "there are only a few experts who can make a steal, high-rise building fall into its own footprint. Only demolition technology at it's very best can do so!
 
 Think about that; and then realize that never has any reinforced steal buildings ever fallen unto its own footprint, via fire or whatever -- without many stringent months of planning and controlled placing of high-tech demolitions. Never, ever!  Except on ...