Like Comet Ping Pong, the Pegasus Museum looks like to be on top of the subway tunnels again.

This is the subway map of Washington DC: http://www.charlesbuntjer.com/washington_dc_map_dc_subway.jpg

And here, if you click on the little map with the pictures: http://www.zillow.com/homedetails/3518-11th-St-NW-Washington-DC-20010/472684_zpid/

You see the location on the map.

If you compare these two images it looks like the Pegasus Museum is on the green line going north, when it goes diagonal again at Columbia Heights.

Could this be something? Since Comet Ping Pong was also connected with Subway tunnels. Could they have a little train downstairs which drives people to the location underground?