The Roman arch avoided rigidity totally, retaining each of the masonry in compression, within the keystone on the piers. Stone in compression has excellent strength, plus the Romans created massive arched bridges and aqueducts in substantial numbers. Extending their arch right into a tunnel, they invented the barrel vault, with https://vymaps.com/US/West-Hills-Masonry-VN23008/?id_new=91f028d46d98c5b158f38e36720f8a1f