I have two particular favorite windows. One shows outer space and includes an actual moon rock. The other is the Maryland window. You can clearly see the state flag, and though this photo doesn't show it, at the bottom there is a Baltimore Oriole (the state bird), a Blue Crab, and Black-eyed Susans (the state flower).
There are also many statues and carvings at the Cathedral. Along with the religious figurines are historical figures like President George Washington.
There is SO much to see at the Cathedral that you have to make several trips to take it all in (like the Louvre). From the inside to the outside, from the multiple chapels to the gardens, there is just so much to enjoy! So on your visit to DC, don't forget this gem!