National Gallery of Art East Wing, Central Court, 2004.

This building, by I. M. Pei, is based on a grid of triangles. You can just make out the triangular sections of marble that make up the floor; even the benches arise from the triangular floor grid in sharp-edged blocks. The sculpture in the upper left is by Martin Puryear; the glass wall behind it now showcases a huge piece by Andy Goldsworthy, igloo-like mounds of cut stone, some of which are bisected by the glass, so that part of the piece is inside, part outside.