From our lofty post we can easily distinguish the limits of the city in the days of Tiberius and Caligula, for to the north we turn our faces towards the ruined bulk of the Amphitheatre, now lying amidst fields and gardens, but well within the town walls at the time when Nero entertained the Armenian king Tiridates and shocked his Asiatic guest by himself descending into the arena and deftly performing the usual disgusting feats of a professional gladiator. To westward lies the Bay of Baiae, a semi-circle of glittering water surrounded by low hills amidst which the Monte Nuovo, unknown to the ancients, stands conspicuous. How completely have all traces of splendour and extravagance disappeared from these shores! At fashionable Baiae across the Bay there is nothing visible save a few shapeless ruins over the identity of which scholars dispute; at busy Puteoli there survive to-day but the ruined Amphitheatre, the Temple of Serapis, and the arches of the famous Mole, to prove to wondering posterity how great were the wealth, the population and the magnificence of a spot which is closely associated with all the power and culture of the Roman Empire in its zenith. [Illustration: ON THE BEACH] Of the various fragments of antiquity that are still standing in this district of the Phlegrean Fields, the Mole of Puteoli is undoubtedly the best preserved and the most interesting. So splendidly constructed is this relic of the past, that but for continuous shocks of earthquake the whole breakwater must have survived intact; as it is, more than half the Mole has withstood the wear and tear of centuries of wind and storm. It is built on the model of a Greek pier, a series of arches of massive masonry, acting at once as a barrier against the force of the invading waves and as a means of preventing the silting of the sand. Formed of brick, faced with stone, and cemented with the local volcanic sand, which is consequently known as _puzzolana_, this wonderful breakwater must originally have stretched out into the Bay a total length of twenty-five arches, its furthest extremity being crowned by a light-house. If we could only call up in imagination the Bay of Baiae in the days of the Empire, when its shores were fringed by sumptuous villas of famous or infamous Romans and its expanse was thickly covered with every variety of vessel of pleasure or merchandise, instead of the few fishing boats that now and again flit across its glassy surface, we might better be able to realise the extraordinary episode which is connected with this classical fragment in the little port of Pozzuoli below us. For it was from the Mole of Puteoli to the spit of land we see on the western shore opposite that the demented tyrant, Caius Caligula, constructed his historic bridge of boats across the Baiaean gulf. Every large vessel in the surrounding harbours had been pressed into the service of the Emperor for this gigantic piece of folly,