Halo3: What’s different about Avalanche legendary map?

Bungie own's designers Niles Sankey and Lars Bakken along with artists Mike Buelterman and Jason Sussman have answered a bunch of questions about Avalanche and hopefully between their answers and the accompanying pictures, what Avalanche is will begin to crystallize.

Lars Bakken explains: The basics are the same, but you’ll notice some new additions (man cannons), and some things missing (the interior tunnel between the bases). We also haven’t had any ladders in Halo multiplayer maps since Halo 1, so we had to re-design the interiors of the bases to accommodate that. There are a lot more quick ways to get around the level now, that’s probably the biggest change.