Throughout Roman history the Janiculum has suffered many alternations of peace idyllic and of sanguinary strife, for it is a natural garden, and it is also the key to Rome. Whoever can hold the terraces of San Pietro in Montorio and the heights to the north and south has the city at his mercy. At the present day the Villa Pamphili-Doria and the Villa Garibaldi crown its summit and stretch downward toward the west, and its southeastern slope, leading toward the Tiber, once contained the gardens of Julius Caesar – those gardens where he received Cleopatra and which he left by his will to the Roman people. One of the earliest chapters in Roman history tells how Lars Porsena came over the Janiculum to reinstate the Tarquins, and one of the latest recounts the struggle carried on across its heights and terraces in Garibaldi’s defense of the Mazzinian Roman Republic. Like the gardens of Ischia and the vineyards on Vesuvius, which are forever threatened by earthquake or eruption, the Janiculum villas will have, so long as war lasts, a precarious existence; but with villas, gardens, and vineyards, so great is the fertility of the soil and so enchanting the prospect, while the world endures men will take the risk.
The water for this part of the city was brought to Rome by the Emperors Augustus and Trajan. Trajan built the aqueduct bearing his name; and this aqueduct, like that of the Virgo, has, in spite of many vicissitudes continued to supply Rome with a varying quantity of water from that time until the present day. The Emperor brought the water thirty-five miles from Lake Rracciano to the Janiculum. It was almost the last water brought to Rome and entered the city at the level of two hundred and three feet above the sea. The first water (the Appian) had entered Rome fifty feet under ground. Trajan used the water from the springs about Lake Rracciano, not from the lake itself, because the spring-water was much purer and the ancient Romans were fastidious in the water they used. Alsietina water, for instance, brought to Rome by Augustus, was considered fit only for baths and the naumachiae; and Frontinus says that, as a matter of fact, the water was intended for that purpose only and for the irrigation of the gardens across the Tiber. Christian Rome was far from being so particular, and its inhabitants drank Tiber water as late as Michelangelo’s time.