The arches of this period are semicircular and usually highly stilted.
Slabs or two small walls; the semicircular space thus formed has a diameter of about 45 ft., and was probably intended for sacrifices.
The severe west front is relieved by three rows of semicircular arches, and has a central porch (there were at one time three) supported by huge red marble lions, sculptured no doubt with the rest of the façade by Giovanni Bono da Bissone in 1281.
A broad semicircular pectoral surmounted by the head of a lioness, and on the left arm a basket.
A semicircular or semi-elliptical pit (calcarone) about 33 ft.