Exposing the layers of history in cityscapes

I really liked this talk on "Time, History and the Internet" because it touches on lots of things I'm interested in.

I have a on-going fascination with the idea of exposing the layers of history present in any cityscape.

I'd like to see content linked to and through particular places, creating a sense of four dimensional space/time anchored specifically in a given location. Discovering and displaying historical content marked-up with the right context (see below) gives us a chance to 'move' through the fourth dimension while we move through the other three; the content of each layer of time changing as the landscape changes (and as information is available).

Context for content: when was it written? Was it written/created at the time we're viewing, or afterwards, or possibly even before it about the future time? Who wrote/created it, and who were they writing/drawing/creating it for? If this context is machine-readable and content is linked to a geo-reference, can we generate a representation of these layers on-the-fly?

Imagine standing at the base of Centrepoint at London's Tottenham Court Road and being able to ask, what would I have seen here ten years ago? fifty? two hundred? two thousand? Or imagine sitting at home, navigating through layers of historic mapping and tilting down from a birds eye view to a view of a street-level reconstructed scene. It's a long way off, but as more resources are born or made discoverable and interoperable, it becomes more possible.