Swampoodle was an Irish neighborhood in Washington, D.C. on the border of Northwest and Northeast in the second half of 19th and early 20th century. This neighborhood is no longer known as Swampoodle and has been replaced in large part by NoMa.
Hopsccotch Bridge is the H Street Bridge (colloquially known as the "Hopscotch Bridge" because of modern art on the bridge which depicts children playing hopscotch). This bridge connects H Street NE to North Capitol Street, and is the western teriminus of the much talked about and finally opened Benning Road Line of the DC Street Car.
If you can find a hole in the artwork, or maybe just around the corner from the posted coordinates find a section low enough to look over, you can see the back side of Union Station and associated Rail Yard.
To log this find, upload a picture of yourself with the rail yard in the background. Alternatively, a picture with the Hopscotch Kids artwork.
To get to GZ you'll need to park elsewehere and walk, or take a bus or streetcar.