I actually found a prototype map that I used to test the large room technique by increasing the size of textures more ten times of the original. It was the map that made me keep going with the idea of creating huge maps in HL (similar technique as in all those CS maps where you're feeling like the size of an ant).
And, as a bonus, I found a Halfquake 1 test map, experiments by TheAwake and another Halfquake Sunrise testing area. I hope you enjoy it!
(Now with exciting stereo sound!)