In the third, after the Campagna, by a great general uplift, had become a land surface, volcanic energy found an outlet in comparatively few large craters, which emitted streams of hard lava as well as fragmentary materials, the latter forming sperone (lapis Gabinus) and peperino (lapis Albanus), while upon one of the former, which runs from the Alban Hills to within 2 m.
The tufa, sperone and peperino were easy to quarry, and could be employed by those who possessed comparatively elementary tools, while travertine, which came into use later, was an excellent building stone, and the lava (selce) served for paving stones and as material for concrete.
The subsoil too is differently formed: the surface consists of very absorbent materials, then comes a stratum of less permeable tufa or peperino (sometimes clay is present), and below that again more permeable materials.
Remains of the walls of the lower town, of the cella of a temple built of blocks of peperino, and also of later buildings in brickwork and opus reticulatum, connected with the post-station (Aricia being the first important station out of Rome, cf.
Of Etruscan sarcophagi there are numerous examples in terracotta; occasionally they are miniature representations of temples, and sometimes in the form of a couch on which rest figures of the deceased; one of these in the British Museum dates from 500 B.C. The earliest Roman sarcophagus is that of Scipio in the Vatican (3rd century B.C.), carved in peperino stone.
No traces of the ancient city, except of its necropolis, the tombs of which are overlaid with a stratum of peperino 3 ft.
The lapis Albanus is a green grey volcanic stone with black and white grains in it (hence the modern name, peperino), much used for building material.