This mod is now part of NVEC - New Vegas Enhanced Content by hairylegs222. You can find it here: http://newvegas.nexusmods.com/mods/44204.

Summary:

At a certain point in the game, Benny can run through some rooms containing Yes Man and travel down to the basement where he escapes into Vault 21. While the Vault 21 tunnels exist and are in the same cell as Vault 21, it is mostly unfinished with no real connection in between the tunnel and Vault 21. The in-game lore said that Mr. House filled in large portions of Vault 21 with cement after he won a bet. I wanted to explain how Benny's escape was possible so I changed the cell a bit. First, I made the tunnel have a more excavated/blown up look as I doubt Benny would have wasted much time digging if he didn't have to. I added floodlights and a new room containing all the excavated dirt. I also moved all the lootable containers into one area so that no one will miss anything. I connected the excavated tunnel to Vault 21 through a vent near the entrance. I've tried to make it one way so that someone doesn't stumble into this area prematurely. Finally, I've moved the entire section so that it aligns correctly in the space between the Vault and the Tops. Please enjoy!

Version History:

v0.2 - fixed some visual errors, added some support beams, and redid the vent entrance.
v0.1 - Initial Release.

Requirements:

Nothing other than New Vegas.

Credits:

The New Vegas Uncut mods by moburma80 - made me think about other things that should be restored.