Sci-fi Idea #1

I'm titling this post Sci-fi idea #1 in the hopes that there will be more than one. It's a bit like having a first annual event. How do you know it will be annual yet? You don't, but you hope. So I was reading Atlas Shrugged for the first time in years and I got to chapter four, which begins like this

Motive power—thought Dagny, looking up at the Taggart Building in the twilight—was its first need; motive power, to keep that building standing; movement, to keep it immovable. It did not rest on piles driven into granite; it rested on the engines that rolled across a continent.

If you don't know, the Taggart Building is the main office of a giant railroad company, and that got me thinking: what if there was a building that actually did rest on engines, roll across the continent or some other fantastic idea like that?  So idea #1 is a kinetic building. The stationary part of the structure would sit high above the ground, and the legs would move so that as someone approaches they would get out of the way. Now what I'd really like to see is a city full of these things so that anyone can get to any building by walking as the crow flies.

And of course once you're thinking about moving buildings and cities of moving buildings, the really crazy ideas start to fly. What about a city that migrates? What about a city that reorganizes throughout the day? You could have neighborhoods that have restaurants next to them at dinner time, bars late at night, and office buildings during the day.When buildings are as free to move as humans, the ideas behind transportation would get very interesting.

So, if any sci-fi writer wants to take this idea and run with it, go for it. Or (way more likely) if someone wants to point me to some sci-fi with a good story where this has already happened that would be cool too.