If you're looking for a fun and educational excursion in New York City, check out the Transit Museum. ER and I spent several hours there yesterday and could have stayed longer if they hadn't been closing for the day. It is located in a decommissioned subway station in downtown Brooklyn. The heart of the museum is down at the track level -- there is a collection of subway cars from all periods of subway history (from the original 1904 trains to the "Redbirds"), and visitors are free to walk around in them, sit down, etc. Each train is decorated inside with actual advertisements and maps from the particular period, so we got to grimace at the kind of '50s ads featured in The Feminine Mystique, and scrutinize old subway maps to learn about discontinued lines such as the H (now the Brooklyn part of the C) and the 8 (the Third Avenue El in the Bronx, now torn down). There is also a working "signal tower" (the control room is called a "tower" by analogy to above-ground railroads) where we could look at a map of the tracks in the vicinity and watch the flashing lights representing actual trains.
One level up there are complete sets of tokens and turnstiles from the last 100 years, buses and trolleys that we could drive (except they didn't go anywhere), and an exhibit on how the original subway tunnels were built. Sandhog is not high on my list of future career choices, but we all owe a great deal to their labor.