"L'ull del temps" is a tool developed by BetaPortal, of the Institut Cartogràfic i Geològic de Catalunya (ICGC) that presents the territory as it is currently and how it was at 1945 (or 1956 to choose) moving the mouse on the screen. You can change the background order and the year of display of old photographs display.  

It is a wonderful example about how it is possible to create stunning tools with web technology of open code and imagination. 

The direct access to the application is http://betaserver.icgc.cat/visor/catalunya_ull_del_temps.html and you can know more in  http://betaportal.icgc.cat/wordpress/catalunya_ull_del_temps/