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, so that the inhabitants of Rome were seriously inconvenienced by the detention of their corn ships, and loud in consequence were the complaints of the Roman populace, for whose anger, it is needless to state, the Emperor cared not a fig. “History,” says Gibbon, “is but a record of the crimes, follies and misfortunes of mankind;” and this smiling Bay of Baiae will ever be memorable as the scene of what was perhaps the worst exhibition of tyrannical caprice that the world has yet witnessed.