I spent Halloween afternoon over in New York's West Village, being given a tour of a gut-renovated townhouse by one of the home's owners. While a description of the actual house will appear next spring in an article I'm writing for another publication, what struck me most was the opening half of the home tour. The homeowner and I stood there alone in the downstairs kitchen, as I listened to her describe what used to be there: the walls that got taken down, the halls that no longer exist, the lost backyard and the missing stairs. We were surrounded by a halo of absent spaces, rooms that had been cut out around the edges and removed. 
And it seemed that you could put together a long and fascinating series of home renovation interviews, with people describing, from memory, the missing architecture around them: where rooms used to be, perhaps entire buildings. It'd be as much an architectural podcast as an experiment in narrative neurology: how former buildings are remembered and described.
I have no idea how long this sort of thing could sustain anyone's attention, to be honest; but what might be called oral histories of missing space could extend from demolished buildings to whole war-destroyed towns, from renovated suburban homes to newly partitioned spaces in a nearby office high-rise. The point would be to tour buildings based only on what those buildings used to be.
In a sense, it's the appeal of ruins.
Perhaps you go on a camping trip to a distant country, where you hike deep into the desert, heading for a series of abandoned villages beyond the mountains northwest of the airport. They are Roman sites, some say, but others suggest a 2500-year old fringe culture outside imperial reach. Either way, as the group of you sits down to cook dinner around a fire—flames lighting up a circle of illegible building forms eroding back into sand—your guide starts to tell a story. The only thing he's describing, however, is an imaginary building that looms around you, he says, on all sides, with rooms, spiral stairways and halls, and the occasional door resting alone somewhere in the darkness, that no one has yet to open. Temples form in the outline of his story: things that used to be but are no longer. The description goes on for hours. You realize, when the moon disappears behind the mountains and your campfire has burned out, that you've been taken several hundred rooms deep into some massive, impromptu architectural edifice produced on the spot by the guide.
Perhaps it could become an alternative oral tradition: buildings handed down, generation after generation, to form a kind of speculative-architectural harddrive inside of which a culture stores its myths. Great events remembered by the rooms they supposedly occurred within.
In any case, it also seems like an interesting opportunity for an iPhone app... Instead of a Phantom City of the unbuilt avant-garde, it's a removed city of the various rooms that used to be there. You could walk into any building in the city and get descriptions and floorplans of the spaces that no longer exist. Renovation detector. Your phone starts to beep as you walk through missing walls.
