Build an arch and explore catenary curves, which form naturally when you suspend a chain or rope by its ends. The top of the chain is almost vertical because it is pulled down by the links below. As you move toward the bottom, the slope of the chain decreases because the links support less weight.
Catenary arches are very strong because they redirect the vertical force of gravity into compression forces that press along the curve, holding the arch’s building blocks in place. The 630-foot Gateway Arch in St. Louis, Missouri, is a catenary arch.