To watch int DC, Union Station must be a stop. My first trip to Union Station revealed a station that saw much better times. The roof leaked and it could use a sprucing up. The last time, I was there, the station had been restored and it was a momument to its former self. It was not only restores, it was now a mall, with real trains.
The only problem is watching trains. The train comes into the station from the south by way of a tunnel. The northern approach end in a terminal settting, expect for the through. The platforms prevents view from the parking deck built above the tracks in the rear.
Just north of Union Station is a Metro Station, above ground. Great! However, all traffic would be not at speed because of entry or exit from the station. Before the Metro, I used to go to New Carolton to watch. This gave me the advantage of speed on the through trains and also the Metro. We have the Metro, in Alexandria, as well. I could go to New Carollton and watch a while and then return to DC to watch until time to depart south. I laid out several possibllites and thought that the following would be the best alternative. The second alternative is to go on to Baltimore and watch the Maryland Commuter and Amtraks there. I could ad to the trip, the watching of the light rail.