The remains of ancient Rome may be classed in three different periods. Of the first, the works of the kings, embracing a period of two hundred and forty-four years, from the foundation of the city by Romulus to the expulsion of Tarquin, very little have escaped the ravages of time; the Tullian walls and prison, with the Cloaca Maxima, being the only identified remains. Of the works of the republic, which lasted four hundred and sixty-one years, although the city, during that period, was more than once besieged, burned, and sacked, many works are yet extant:—the military ways and aqueducts, and some small temples and tombs. But it was during the third period, that of the emperors, that Rome attained the meridian of her glory. For three centuries all the known world was either subject to her, or bound by commercial treaties; and the taste and magnificence of the Romans were displayed in the erection of temples to the gods, triumphal arches and pillars to conquerors, amphitheatres, palaces, and other works of ostentation and luxury, for which architecture was made to exhaust her treasures, and no expense was spared to decorate. Architecture was unknown to the Romans until Tarquin came down from Etruria. Hence the few works of the kings, which still remain, were built in the Etruscan style, with large uncemented, but regular blocks. In the gardens of the convent Giovanni a S. Paolo is a ruin of the Curia Hostilia, called the Rostrum of Cicero; and some few fragments, also, remain of a bridge, erected by Ancus Martius. On this bridge (Pons Sublicius) Horatius Cocles opposed singly the army of Porsenna; and from it, in subsequent times, the bodies of Commodus and Heliogabalus were thrown into the Tiber. In the pontificate of Nicholas V. it was destroyed by an inundation. There are also the remains of a large brick edifice, supposed to have been the Curia, erected by Tullus Hostilius, which was destroyed by fire when the populace burned in it the corpse of Clodius. Julius Cæsar commenced its restoration; and Augustus finished it, and gave it the name of Curia Julia, in honour of his father by adoption.