The public works which he completed were great and essential rather than numerous; they were in particular the following: an aqueduct begun by Gaius ; also the outlet of Lake Fucinus and the harbour at Ostia, although in the case of the last two he knew that Augustus had refused the former to the Marsians in spite of their frequent requests, and that the latter had often been thought of by the Deified Julius, but given up because of its difficulty. He brought to the city on stone arches the cool and abundant founts of the Claudian aqueduct, one of which is called Caeruleus and the other Curtius and Albudignus, and at the same time the spring of the new Anio, distributing them into many beautifully ornamented pools. He made the attempt on the Iucine Lake as much in the hope of gain as of glory, inasmuch as there were some who agreed to drain it at their own cost, provided the land that was uncovered be given to them. He finished the outlet, which was three miles in length, partly by levelling and partly by tunnelling a mountain, a work of great difficulty and requiring eleven years, although he had thirty thousand men at work all the time without interruption. He constructed the harbour at Ostia by building curving breakwaters on the right and left, while before the entrance he placed a mole in deep water. To give this mole a firmer foundation, he first sank the ship in which the great obelisk® had been brought from Egypt, and then securing it by piles, built upon it a very lofty tower after the model of the Pharos at Alexandria, to be lighted at night and guide the course of ships.