When landscaping the U.S. Capitol grounds in 1874, Olmstead wanted to create things that were both aesthetic and functional. The walls were low so the public could see over them. Lanterns like the one shown above lit the grounds at night. The fountains now even have meters to lower the water pressure in heavy winds. Modern architects now call this type of landscaping as handscaping.
This photo is on the west side by the Peace Monument where many tour groups meet their bus. It’s a typical corner of the wall with a good look at the lantern.