The materials used in constructing these structures are greater proof to the great contrast in their designs. The reinforced concrete Harvard Stadium was built mostly from tall slabs of concrete, and even the bleachers are simply concrete blocks. The Colosseum was made from a great variety of materials including travertine, tufa, brick, and cement. Most of the outside was made from travertine and tufa, with much of the interior of the structure made from bricks and arches from concrete.