The first part of the second century was distinguished by the splendid architectural achievements of the reign of Hadrian (117-138 A.D.) in Rome and the provinces, especially Athens. Nearly all his works were marked by great dignity of conception as well as beauty of detail. During the latter part of the century a very interesting series of buildings were erected in the Hauran (Syria), in which Greek and Arab workmen under Roman direction produced examples of vigorous stone architecture of a mingled Roman and Syrian character. The most-remarkable thermæ of Rome belong to the third century--those of Caracalla (211-217 A.D.) and of Diocletian (284-305 A.D.)--their ruins to-day ranking among the most imposing remains of antiquity. In Syria the temples of the Sun at Baalbec and Palmyra (273 A.D., under Aurelian), and the great palace of Diocletian at Spalato, in Dalmatia (300 A.D.), are still the wonder of the few travellers who reach those distant spots. While during the third and fourth centuries there was a marked decline in purity and refinement of detail, many of the later works of the period display a remarkable freedom and originality in conception. But these works are really not Roman, they are foreign, that is, provincial products; and the transfer of the capital to Byzantium revealed the increasing degree in which Rome was coming to look to the East for her strength and her art. [Illustration: FIG. 53.--TEMPLE OF VENUS AND ROME. PLAN.] +TEMPLES.+ The Romans built both rectangular and circular temples, and there was much variety in their treatment. In the rectangular temples a high _podium_, or basement, was substituted for the Greek stepped stylobate, and the prostyle plan was more common than the peripteral. The cella was relatively short and wide, the front porch inordinately deep, and frequently divided by longitudinal rows of columns into three aisles. In most cases the exterior of the cella in prostyle temples was decorated by engaged columns. A barrel vault gave the interior an aspect of spaciousness impossible with the Greek system of a wooden ceiling supported on double ranges of columns. In the place of these, free or engaged columns along the side-walls received the ribs of the vaulting. Between these ribs the ceiling was richly panelled, or coffered and sumptuously gilded. The temples of +Fortuna Virilis+ and of +Faustina+ at Rome (the latter built 141 A.D., and its ruins incorporated into the modern church of S. Lorenzo in Miranda), and the beautiful and admirably preserved +Maison Carrée+, at Nîmes (France) (4 A.D.) are examples of this type. The temple of +Concord+, of which only the podium remains, and the small temple of Julius (both of these in the Forum) illustrate another form of prostyle temple in which the porch was on a long side of the cella. Some of the larger temples were peripteral. The temple of the +Dioscuri+ (Castor and Pollux) in the Forum, was one of the most