In the year 144 B.C., Q. Marcius Rex constructed the Aqua Marcia, one of the noblest of the Roman monuments, sixty-two miles in length, seven of which were on arches, sufficiently lofty to supply the Capitoline with pure and cold water. Seventeen years after, the Aqua Tepula was added to the aqueducts of Rome. [Sidenote: Triumphal Arches.] The first triumphal arch erected to commemorate victories was in the year B.C. 196, by L. Sertinius. Scipio Africanus erected another on the Capitoline, and Q. Fabius, B.C. 121, raised another in honor of his victories over the Allobroges. This spanned the Via Sacra where it entered the Forum, and at that time was a conspicuous monument, though vastly inferior to the arches of the imperial regime. [Sidenote: Temple of Concord.] [Sidenote: Basilica Opimia.] When tranquillity was restored to Rome after the riots connected with the murder of the Gracchi, the Senate ordered a Temple of Concord to be built, B.C. 121, in commemoration of the event. This temple was on the elevated part of the Vulcanal, and was of considerable magnitude. It was used for the occasional meetings of the Senate, and contained many valuable works of art. Adjoining this temple, Opimius, the consul, erected the Basilica Opimia, which was used by the silversmiths, who were the bankers and pawnbrokers of Rome. The whole quarter on the north side of the Forum, where this basilica stood, was the Roman exchange-- the focus for all monetary transactions. [Sidenote: Private palaces.] [Sidenote: Houses of the nobles.]