This mod adds a Vault door behind Megaton that takes you to Sanctuary Hills. Right now its just a copy of Tranquility Lane but i added an interior to a house to make it as much like the house shown in the E3 demo as i possibly could. This is my first mod so its not perfect.
Installation:
Drag and drop into Data folder in your fallout 3 directory
Make sure you have it activated
Vault door is not on the inside of Megaton, it is behind on the outside.

If you want to share any ideas with me for future mods send me a message on Twitter @Blade2692 as i dont come on the nexus much to see messages.