From The TimeSplitters Wiki

Bunker
Size	Medium
Location	Underground in an abandoned military bunker
Climate	None (It seems to be dusk when one looks up the manhole)
Unlockable	Unlocked by Default
Recommended Bots	N/A
Recommended Weapons	N/A

The bunker was introduced in TSFP and has a sort of dark and lonely feel to it. It is a very confusing map to navigate with many blind corners and doors. Despite it's confusing layout, it's a very good map for Capture The Bag due to the bags being a fairly straight line across from one another.