Map format

Hi there,
I want to create a program to walk through a 3d world. I want to use an existing map format, because i don’t want to write a map building tool, too.
Does anybody know, which map format to use best (indoor and outdoor maps) and where to get detailed information about that format?

Quake 3 Docs can be found here:

It is better used for indoor maps.

Okay… fine… thanks…
anyone else?
some more information perhaps…

Does anybody know a good site for q1 map loader ???

Q2 maps might be a bit simpler to use, otherwise look at the unreal/UT exported text format it is fairly easy to understand (although is full of extra info you wont need), or wait until I have finishes my level editor and converter.