ty of structural features. They were moreover
exceptionally successful in the laying out of cities, as proved by the
wonderful groups of buildings in the fora or public squares in which
courts of justice and markets were held, of the capital and other
cities, and by the fine continuous vistas of their streets, in which
irregularities were masked by clever contrivances, adding greatly to the
symmetry of the general effect. Temples, basilicas, baths, bridges,
aqueducts, triumphal arches, palaces, and private houses were all set in
the environment most suitable to them, and even tombs were ranged
according to a definite plan, not, as in most modern cemeteries, dotted
here and there in an arbitrary manner.

[Illustration: Pont du Gard, Nimes]

The earliest Roman works of architecture were of a purely utilitarian
character, and in addition to the Cloaca Maxima already mentioned the
most noteworthy still in existence are the bridges over the Tiber, the
aqueducts of the Campagna outside Rome, and the so-called Pont du Gard
at Nimes, France. The most ancient temples greatly resemble those of
Greece, and amongst them may be named as specially typical those of
Fortuna Virilis and of Antoninus and Faustina, both now in use as
churches, and that of Venus and Rome, all in the capital, that of Diana
at Nimes known as the Maison Carree, and that of the Sun at Baalbec. Of
later date are the beautiful circular temples, of which the grandest
example is the Pantheon of Rome, built under Hadrian about A.D. 117, in
which Roman architecture reached its noblest development. The colonnaded
porch with entablature and pediment, that detracts so much from the
external effect of this magnificent building, did not originally belong
to it, but formed the entrance of a temple built by Agrippa more than a
century before, and was added to the Rotunda after the completion of the
latter. The internal diameter of the Pantheon is 142 feet 6 inches, and
its height at the apex of the dome is the same; its walls are 20 feet
thick, and its concrete dome is adorned with deeply recessed panels or
coffers and has a single circular opening at the crown through which
alone light is admitted. The floor is of marble; bronze pilasters flank
doorways of the same metal, the oldest existing specimens of their kind,
and it is supposed that when first completed the whole of the outside
was cased in white and the inside in coloured marbles.

[Illustration: Section of Pant