Corbelled Arch, Copán
The Maya did not build arches the way European did, with each block leaning into the next and held up by a keystone at the top. Instead, they used a technique called corbelling, in which each block rests on top of the next but is drawn slightly toward the center until the two sides meet. These blocks were then frequently shaved off to form a triangle. The photo shows the arch without further dressing of the stone, while the line drawing shows the process of moving each layer further toward the center.