Rat Race is an underground forerunner facility multiplayer map, that is featured only in Halo: Combat Evolved. The map is generally designed as a circle, with halls connecting to each other, this map consists of two floors. The first floor is the combat area, with some grenades pickups. The second floor can be accessed by teleportng into it, through the three teleporters that are put equally on each of the three parts of the map. When you drop from the second floor, that contains some weapons like a Pistol and a Plasma Rifle, you can pickup a items like the Overshield by falling into them. Or shooting them while on first floor.
The map is also considered small, movement might not be possible with huge number of player. 2-6 is the recommended number of players.
You can pickup these weapons in this map:
You can pickup these items in this map: