This one is amazing. Thanks to the Smithsonian for posting it online. The caption says this is around 1900.
Looking toward the west side of the United States Capitol building, a panoramic view of the city of Washington, D.C. shows the Mall area in the foreground before the railroad tracks were removed. A train is visible on the tracks. The domed structure in front of the Capitol is the Botanic Garden original octagonal greenhouse of 1859 and behind it the central pavilion added after the Civil War. The buildings were razed in 1932. The Botanic Garden was on a site previously occupied by the Columbian Institute for the Promotion of Arts and Sciences in Washington, D.C.