Narrows

Long and Lean is a multiplayer map for Halo 3.

Discovery
The level codenamed Long and Lean was mentioned in the third Bungie podcast. It's only description is having a "very special weapon in the middle". Which may be a Gravity Hammer, Fuel Rod Cannon or other such heavy weapons worth risking a life in the middle. Nothing else has been revealed.

Speculation
Long and Lean may describe a long but thin map, a quite possible reincarnation of Longest, Coagulation, or a completely new map as it may be large if it is long and thin to provide dynamics.