I took this photograph of the Neue Nationalgalerie in Berlin twenty years ago. This roof, a two way structural steel system, weighs 1250 tons. This photograph presents one of the eight columns that support it. On top of the column and beneath the roof occurs the only curved lines in the entire structure that I know of. This is the point at which the weight of the roof transfers through to the columns and down to foundation. The element is not one piece. It is formed from two pieces one male and one female. The female piece is the one on top. The diameter through which the loads are passing is no more than 7 inches (18cm). That's an approximate surface area of 39 square inches. The bearing stresses at this point are thus 64,102 pounds per square inch, well within the proportional limit for standard structural steel. The element appears to project a dark golden light. Which is to say the element as a whole holds in equilibrium two and a half million pounds all day everyday.