Chicago-L.org will be hosting its 7th annual tour of “L” stations next month, visiting various stations by old-school train cars and offering lectures on CTA architecture and history. Reservations are required and can be made via this form [PDF], which also provides the tentative itinerary. Experience past tours virtually here. Or, if you're not quite a trainspotter, but you're still mildly interested, check out the Loop Tour Train. It's touristy, but free, and it runs Saturdays through the end of September.