These two aqueducts were made together, or were so closely connected that we cannot separate their history, although they were not the same water; the Anio Novus came from some miles higher up the river Anio than the Claudia. The latter was, like the previous aqueducts, taken from springs, that were intercepted before they fell into the river Anio; but the Anio Novus was part of the river itself, in which a gigantic loch was made by building a great wall across it, about a hundred yards in front of a natural waterfall, and forcing the water to flow over it, forming a magnificent cascade, and at the same time causing some of the water to flow through the _specus_ which was cut in the cliff by the side of the river, at a rather lower level than the top of the wall. The sources of the Claudia are below this cascade, those of the Anio Novus are above it. The line of each of these aqueducts is distinct in all the early part of its course; but after they come down to the valley of the Campagna of Rome, at the Piscinæ, the two are carried on the same fine lofty arcade into Rome. These were the highest, and passed over the Marcian arcade with the three aqueducts upon it. They form the finest feature in the landscape on the eastern side of Rome. The sources are above Subiaco, and in what is considered by artists as some of the most picturesque scenery in the world. The photographs illustrating this are very numerous, the subjects being some of the best that can be imagined for this purpose. The history of these two most important aqueducts can now be better seen in this series of photographs than in any other manner, and better understood than by any written description of them, after the outline of their history is once given. They were begun in the year of Rome 789, A.D. 38, under the Emperor Caius Cæsar, or Caligula; carried on and completed by his successor, Claudius, in the year of Rome 803, A.D. 52. They were therefore fourteen years in construction, according to Frontinus[229]; but Nero was then married to Octavia, he was the actual governor of Rome, and he carried on the great work upon what are called the Arches of Nero, along the Cœlian Hill, as far as the arch of Dolabella, where a large reservoir for this water was built. This work was afterwards carried on by his successors in three branches, one to the Colosseum, a second to the Palatine, and over it to the Capitol, and a third to the Aventine. Frontinus himself, who has left us his admirable treatise on the subject, had the direction of these works for many years; he was Curator Aquarum under the Emperors Nerva and Trajan, and some of the greatest works were done in his time,—at his suggestion, and according to his plans.