The Capitol with one of the reflecting pools in the foreground. Everything in the mall looks close together, but when you start to walk you realise how massive it is. It is almost 2km end to end; easily long enough for a runway to land a Boeing 737.
However there is so much to see on the mall; it is surrounded by interesting museums. You could easily spend a week just in the museums. I highly recommend both the aerospace museum, and the museum of American history.