Tricky ways to pull down a skyscraper

Some day nanobots will eat our old buildings and excrete the recycled materials where we are building anew. But until then, we need Japanese engineers to figure out how to do the job safely and efficiently. Frankly, this video suffers from way too much reporter talking head syndrome... show me the action! But if you skip to the time-lapse footage of the two methods described--basically, top down and bottom up--wow, way cool (roughly minutes 2:00 and 4:00).