Spooky things to do in Baltimore?

I'm taking a group of 11-15 year olds in a youth group at our church to go to Baltimore for a day, and since we would be there late October, I thought we could focus on 'spooky history' of Baltimore, and do things like visit the Edgar Allen Poe house and do the Fell's Point Ghost Walk. Are there other things that come to mind? Or just in general, what kind of advice do you have for going to Baltimore, what are some cheap, touristy things you can do in B-More (other than the aquarium, too expensive)?

Some aren't spooky but still interesting. Here's a couple of links:
http://www.baltimoretours.net/
http://baltimore.org/group-tour
http://www.baltimorerent-a-tour.com/
http://www.borail.org/

walk through the hood at 0100 am and guarantee results lol