22/8  eRuv - I particularly like the thought of "Public Places - Private Spaces"

Category: QR Code, Data Matrix...    By editor at 01:11
eRuv: A Street History in Semacode
eRuv (pronounced ey-roov) is a digital graffiti project installed along the route of the former Third Avenue elevated train line in lower Manhattan. The train line, dismantled in 1955, was more than just a means of transport; it was part of an important religious boundary — an eruv — for a Hasidic community on the old Lower East Side. Using semacodes, the former boundary is reconstructed and mapped back onto the space of the city. Pedestrians with camera phones can then access location-specific historical content linked through the semacodes.
See eRuv photos. Each semacode links to an archival photo of the train line from that specific location.

See also:
Sophie Calle's Public Places - Private Spaces