The Romans based much of their architecture on the domes. Domes permitted the construction of vaulted ceilings, and could cover large public spaces. The Pantheon in Rome has a concrete dome with an oculus opening to the sky. The light from the oculus moves around this space in a sort of reverse sundial effect. The oculus also serves as a cooling and ventilation method. During storms, a drainage system below the floor handles the rain that falls through the oculus.