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					Originally Posted by Alex  Read the comments to see how common such stairs are in older construction (including being part of the reason you can no longer tour the upper floors of Monticello). Found that little unknown bit of architectural learning interesting. | 
	
 While 
alternating tread stairs (also called "monk's ladders") have been around forever, and are quite safe, they are nothing like the ones in the OP.  Those are mayhem just waiting to happen!