my basement space

With a space that large, the options are nearly infinite.  My initial thought is you can make a large E shaped layout with an extra "middle tine" of the E.  The long side of the E would be the long wall on the left of the diagram.  Then you could have the tines of the E coming out at the top (to the boiler room), the bottom, and to the 2 support comluns.  Such a layout would mean a lot of benchwork and track, and assumes you want to use most of the basement, but it would keep you busy for years.

This one might be fun to build and fun to run ;

http://mainlinehobbies.com/blo...3-x-12-lionel-layout

Get a hold of Matt Jackson, he loves that stuff. He will whip something nice for you.

I appreciate the vote of confidence, John. You're right; I do like a challenge.

Train Man:

Are you planning on running conventional (transformer handles) or using command control (DCS and/or TMCC)? Command control makes operation easier and more realistic. Also, what type of equipment do you want to run -- scale sized, semi-scale, or BIG scale sized equipment like auto racks, piggy-backs, and big steam?

The down side of too many mainlines is that you lose space for scenery and it makes your layout look smaller. I'd recommend no more than two mainlines and use cross-overs and the occasional siding to allow high-priority/express trains to pass locals.

With your space and the wall configuration, you can do wider curves (something you start losing with more mainlines) without needing to do the normal "around the walls" design.

As to the boiler room, what kind of access do you require? Where is the door?