View from Vaekero near Christiania, by Johan Christian Dahl. Christiania is present-day Oslo, and Dahl, as some of you may infer (after reading Boy), is Norwegian. He is also famous for Two Men Contemplating the Moon.
Houses on a Hill, Paul Cezanne.
I also rather like his “The Bend in the Road”
Another great Romantic one I like, this time by an Englishman, was
Venice: The Dogana and San Giorgio Maggiore, Joseph Mallord William Turner
A more contemporary, Esplanade underpass-style one is
Mas Voeux, Annette Messager. Couldn’t find the exact picture of the one in the National Gallery, which has vows in French in different coloured ink.
And of course the Calder Mobiles:
Liangze took the camera with him to the Library of Congress, so I have no pictures. Suffice to say I really enjoyed the National Gallery. The walkway connecting the East and West wing was super swanky: