Charlie, That big HO layout you remember was a casualty of the roof collapse, and need for full handicapped access as reconstruction took place. It had been located on a floor that there was no way to make handicap-accessible at reasonable cost. The museum has a replacement HO layout in a former C&O coach. The Holiday Festival of Trains is a special event, and several train clubs set up in the roundhouse during the Holiday Season. The National Capital Trackers have been setting up for several years, and this year the dates are 12-22 through 12-29. Other displays are from MTH trains, the Baltimore N-Trak club, Baltimore American Flyer club, and others in the past. You won't see these unless you visit during the Holiday Season.
What are you doing this weekend? How about a road trip to Baltimore? LOL
Hours Saturday are 10-4, Sunday 11-4.