Another thing I'm struggling with is how to integrate the display of time (basically a linear string with events on it) with space (messy, 3-d). I would like a zoom feature here too, so that you could, for instance, view a line representing all events on the European continent, then be able to zoom in and separate by country, then maybe by city, etc.
I don't really want to get all complex with geographical views, since that would involve getting into 3d rendering. For a first pass, it would probably suffice to separate out the timelines side-by-side. Although... it may be neat to have a 2d map at the bottom with the timelines growing out of it. As you zoom, the map zooms too - but now you really are talking about another API, and lining stuff up on the screen. But it would be a very graphical way to show the geographical proximity of various events and timelines.