It is believed that the Sumerians invented the arch somewhere around 6000 B.C. The Romans, however, receive much of the credit for perfecting the design.
Arches have been used in the architecture of ancient societies for thousands of years, so it is difficult to know exactly who invented arches. Sumerians receive the credit based on the appearance of arches in ancient aqueduct ruins. Romans figured out to reinforce the arch so that weight placed on it could be more evenly distributed. They reinforced the midsection by adding concrete, a Roman invention and that is primarily credited with the durability of Roman structures. The foundation of the arch is the keystone, which acts as the pivotal stone that distributes weight throughout the structure based on the pressure placed on top of it. Because the stones of an arch need to fit together tightly, concrete helped seal the seams between them. The Romans also figured out that repeating arches at regular intervals support the construction of large structures, such as the Colosseum of Rome. Romans also flattened the design of arches from those originally designed by earlier civilizations. They used Greek column design and spacing to calculate the ideal width of an arch to optimize weight distribution.