15. Above the rostra was the Senate-house, said to have been first erected by Tullus Hostilius; and near the Comitium, or place of meeting for the patrician Curiae.[17] This area was at first uncovered, but a roof was erected at the close of the second Pu'nic war. 16. The Cam'pus Mar'tius, or field of Mars, was originally the estate of Tarquin the Proud, and was, with his other property, confiscated after the expulsion of that monarch. It was a large space, where armies were mustered, general assemblies of the people held, and the young nobility trained in martial exercises. In the later ages, it was surrounded by several magnificent structures, and porticos were erected, under which the citizens might take their accustomed exercise in rainy weather. These improvements were principally made by Marcus Agrippa, in the reign of Augustus. 17. He erected in the neighbourhood, the Panthe'on, or temple of all the gods, one of the most splendid buildings in ancient Rome. It is of a circular form, and its roof is in the form of a cupola or dome; it is used at present as a Christian church. Near the Panthe'on were the baths and gardens which Agrippa, at his death, bequeathed to the Roman people. 18. The theatres and circi for the exhibition of public spectacles were very numerous. The first theatre was erected by Pompey the Great; but the Circus Maximus, where gladiatorial combats were displayed, was erected by Tarquinus Priscus; this enormous building was frequently enlarged, and in the age of Pliny could accommodate two hundred thousand spectators. A still more remarkable edifice was the amphitheatre erected by Vespasian, called, from its enormous size, the Colosse'um. 19. Public baths were early erected for the use of the people, and in the later ages were among the most remarkable displays of Roman luxury and splendour. Lofty arches, stately pillars, vaulted ceilings, seats of solid silver, costly marbles inlaid with precious stones, were exhibited in these buildings with the most lavish profusion. 20. The aqueducts for supplying the city with water, were still more worthy of admiration; they were supported by arches, many of them a hundred feet high, and carried over mountains and morasses that might have appeared insuperable. The first aqueduct was erected by Ap'pius Clo'dius, the censor, four hundred years after the foundation of the city; but under the emperors there were not less than twenty of these useful structures, and such was the supply of water, that rivers seemed to flow through the streets and sewers. Even now, though only three of the aqueducts remain, such are their dimensions that no city in Europe has a greater abundance of wholesome water than Rome.