This project from UCLA lets you overlay historical maps of any one of about twenty cities onto contemporary satellite photos of that same city, all in a Google Maps-based interface. It makes for a fascinating comparative exercise, and doubles as a good reminder that as authoritative as information graphics might seem to be — many of these maps were canonical in their day — they can still be quite subjective and even misleading, especially with the benefit of historical hindsight.

You can play with Hypercities over here.

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