so that just across the road here, we have adolphus w. greeley, one of the early arctic explorers who was here on an army signal corps expedition at the end of the 19th century. went farther north than anybody had been at that time. just down this road is the grave of john wesley powell, who explored the colorado river. he had one arm at the time. he had lost his arm at shiloh in the civil war, but he went on to be a great explorer, and other great things. u.s. geological survey. another part of arlington just over the hill are the arctic explorers, robert gary and his associate matthew, who claim to reach the bowl in 1909. they are here. the point is arlington is more than just a military cemetery. it's a place for explorers, figures from history. and many other things. >> we are on the hill overlooking the city here. what is this tomb on the mound here overlooking the sea? >> this is the tomb of the freshmen who served in the american revolution. he stayed on. he was commissioned to design the city of washington. so he came here in 1891, 1892.