I've never edited wikipedia before so sorry for just sticking this in here, but after a long trip I found the last remaining bridge in Peru and crossed it with a friend this morning. It would help if someone put in the proper spelling, since almost everyone who has heard of it (which is hardly anyone) speaks at least some Quechua - as far as we could figure out it is actually "Q'eswachaka", although we encountered "Queswachaka" and "Qeswachaka". Apparently it literally means 'bridge for soldiers' in Quechua. The (presumably Latinate or in some way Spanish) spelling Keshwa Chaca doesn't really do you much good if you're trying to find anything online.  

 P.S. It was slightly broken and literally terrifying. We took a lot of pictures, and would be happy to upload them once back in Europe.