|The following is based on Van Buren and has not been confirmed by canon sources.|
The New Canaan secret entrance was a location in the New Canaan outskirts.
This is a secret entrance into New Canaan through the junkyard wall. The "stealthy" approach to assassinating Jeremiah Rigdon is to go through this entrance, revealed by Steve.
The New Canaan secret entrance was going to appear in Van Buren, the canceled Fallout 3 by Black Isle Studios.