Scale 1 : 457,000.

Lake Bolsena discharges its surplus waters through the Marta into the Me­di­ter­ra­nean. The fine Lake of Bracciano, to the south of it, gives rise to the Arrone. It, too, appears to be a basin formed by a subsidence of the ground or erosion, and not a crater. The Lake of Vico, on the other hand, clearly occupies an ancient volcano, though its rampart has been gutted towards the east. Close to the lake, and within the encircling rampart, rises Monte Venere, a perfect cone, the gentle slopes of which are luxuriantly wooded. Formerly the lake surrounded this cone, but the breach through which its emissary escapes to the Tiber having gradually been deepened, the waters of the lake subsided. Tradition says that an ancient city lies at its bottom.

On crossing the Tiber we reach the beautiful volcanic group of Albano, within the great crater of which may still be traced the remains of several secondary craters, some of them occupied by lakes. The principal one of these, Monte Cavo (2,790 feet), rises in the very centre of the exterior rampart. Tradition points it out as one of Hannibal’s camps. The exterior slopes of the mountain consist of pozzuolana, small stones, and ashes, through which the torrents have dug out furrows in divergent directions. The diversity of these {261} volcanic products enables us to trace the phases of activity of this Roman Vesuvius, which was active at a much more recent epoch than the volcanoes farther north, and sent its streams of lava to the very gates of Rome.

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Fig. 91.—VOLCANOES OF LATIUM.

From the Austrian Staff Map. Scale 1 : 294,000.

The Lake of Albano discharges its surplus waters through a tunnel 7,665 feet in length, which has been in existence for more than twenty-two centuries. The lake is famous on account of a small crab, large numbers of which are forwarded to Rome during Lent. It is the only species of this animal hitherto discovered in fresh water, and zoologists conclude from this that the crater now occupied by the lake formerly communicated with the sea, but was separated from it by slow upheavals and the ejection of volcanic products. Flint implements and vases of baked clay, discovered in the thick layers of volcanic peperino, prove that at the {262} period of the earliest eruptions the country was already inhabited by a civilised population. Some of the vases referred to are doubly precious, for they present us with delineations of the houses of that prehistoric epoch. Roman coins and clasps of bronze, discovered in the upper layers of lava, prove that these are comparatively recent. In fact, the most diverse developments of civilisation have left their traces in these ancient craters. Alba Longa and other towns of the Latins have been replaced by Roman cities; then came the castles of the popes, and of other high dignitaries of the Church; and at present these hills are one of the chief resorts of the crowds of strangers who flock to Rome from every quarter of the world. On the culminating point of Monte Cavo stood the famous temple of Jupiter Latialis, where the Latins celebrated their federal Feriæ. The last remains of this temple were swept away in 1783, to be used in the construction of a church. From its site the eye embraces a view extending to the hills of Sardinia.

The Lake of Nemi no longer reflects in its bluish waters the foliage of luxuriant trees, or the walls of that dreaded temple of Diana whose priest was only allowed to assume office after he had killed his predecessor in a duel. It, too, has its subterranean emissary, like the Lake of Albano. As to the Regillus, famed for the defeat of the Latins by the Romans, it has dried up, whilst the incrustating Lake of Tartari and that of the Solfatara, with its floating islands, are more shallow ponds, which owe their fame almost exclusively to the vicinity of Tivoli.