Things fall apart.

An excellent set of images here by sculptor Lori Nix, depicting what happens when humans either disappear (zombies, rapture, daleks, badgerpocalypse etc.) or simply abandon their civilisation. These are actually scale model dioramas, harking back to a time when draughtsmanship was every bit as important to art as theory and concept.

http://www.lorinix.net/the_city/index.html

A particular favourite of mine is the detail rendered on the Galaga arcade machine in one image. The derelict launderette meanwhile seems simply very sad.

We've been here before, of course. There were once huge cities around the Nile and in Mesopotamia. Where did they go? They simply crumbled to dust, leaving behind only the sturdiest of stone monuments to mark their passing.