Yes, Sandy, how do you do that? Sincerely, I'm not being a wiseass. Some building types have disappeared over time due to understanding that they don't work any more. Glorious buildings that once were once seen as absolutely the best ever. Forts, for example. Gothic cathedrals that failed after exceeding the limits of stone construction. High rise engineers now admittedly design to the limits of failure under economic pressure and aesthetic ambition. One of the best high-rise structural engineers in the world, often consulted after failures, says that it cannot be known for sure all the forces that a super-high-rise will face, even with the best supercomputer modeling (though not at the capability of Nat Lab nuclear similuations) for each is unique, often purposely unique, that each is an experiment, and there is no testing laboratory except the building itself. Most mid- and super-high-rises require remedial work almost immediately, some even during construction, and sensors are now always installed to provide feedback on what the modeling says cannot be foretold with certainty. Those which have undergone remediation in NYC that I know about are numerous, and most of that has been kept under wraps with NDAs of those designing the corrections, to protect property values as well as reputations and to fend off lawsuits. The New Yorker a few years ago published one of the few accounts not in technical journals about high-rise remediation, in this case about CitiCorp's middling-rise, telling of the years-long attempt to avoid culpability not only by the original structural engineer but by a host of other prominents involved, despite repeated damning studies funded by occupant-leaseholders who could hear the building pop and creak, feel movement and see cracked interior walls. No big deal, perhaps, for unique large architectural and civil structures behave in unexpected ways, having no unique precedent to learn from. The safest high-rises are those that copy successes, and the successes are few for super-high-rises, not many are built. Ok, daring is needed, that is the architect's drug of choice and sale, but recall the building code of Vitruvius: commodity, firmness and delight. The architectural delight drug needs the other two or why bother building at all, just take a pill. The skyscraper bounty of which is in short supply downtown these days. No matter, it will come raging back like a bull on Monday, or will that market crash too.