The hearting is of rubble masonry, and the faces are coursed ashlar.
Grey tufa period; ashlar masonry of tufa, coated with fine white stucco; rubble work of lava.
The design of these entrance gateways is extremely simple and massive, depending for their effect on the fine ashlar masonry in which they are built, the decoration being more or less confined to ornamental disks.
The simple plain ashlar masonry still predominates, but the wall surface is broken up with sunk panels, sometimes with geometrical patterns in them.
The actual construction of successful masonry dams has varied from the roughest rubble masonry to ashlar work.