reached by stopping at the station of the Aquae Albulae, on the Tivoli
line, and following the ancient road which led to the works. This road,
twice as wide as the Appian Way, is flanked by substructures, and is not
paved, but macadamized. Parallel with it runs an aqueduct which supplied
the works with motive power, derived probably from the sulfur springs.
There are also remains of tombs, one of which, octagonal in shape,
serves as a foundation to the farmhouse del Barco.

The most remarkable monument of the whole group is the Roman quarry from
which five and a half million cubic meters of travertine have been
extracted, as proved by the measurement of the hollow space between the
two opposite vertical sides. That this is the most important ancient
quarry of travertine, and the largest one used by the Romans, is proved,
in the first place, by its immense size. The sides show a frontage of
more than two and a half kilometers; the surface amounts to 500,000
square meters. The sides are quite perpendicular, and have the
peculiarity of projecting buttresses, at an angle of 90 degrees. Some of
these buttresses are isolated on three sides, and still preserve the
grooves, by means of which they could be separated from the solid
mass....

In order to keep the bottom of the works clean and free from the
movement of the carts, for the action of the cranes, and for the
maneuvres of the workmen, the chips, or useless product of the squaring
of the blocks, were transported to a great distance, as far as the banks
of the Anio, and there piled up to a great height. This is the origin of
that chain of hills which runs parallel to the river, and of whose
artificial formation no one, as far as I know, had the least suspicion.
One of these hills, visible from every point of the neighboring
district, from Hadrian's villa as well as from the Sulfur Baths, is
elliptical in shape, 22 meters high, 90 meters long, and 65 meters wide.
It can with reason be compared with our Testaccio. It is easy to imagine
how immense must have been the number of blocks cut from the Cava del
Barco during the period of the formation of this hill alone. Another
proof of the antiquity of the quarry, and of its abandonment from
imperial times down to our own day, is given by this fact....

There are three collections of brick-stamps in Rome; one, of little
value, in the Kircherian museum; the second in the last room of the
Vatican library, past the "Nozze aldob