The tunnel of the Alban lake, a wonderful work, is one of the curiosities of Latium; it runs nearly three Roman miles under ground towards the place of its destination, and was intended to carry off the water of the lake, which, when, in consequence of earthquakes, the subterraneous passages had become blocked up, rose above the ridge of the crater and inundated the country. I have already spoken about this extraordinary structure in my History of Rome,[32] and shall, therefore, confine myself to a brief recapitulation. It is difficult to form a clear idea of the matter. Imagine the crater filled to the edge, and bear in mind that it was intended to give to it a level about 200 feet lower. In order to attain this, a line was first drawn in the contemplated direction of the tunnel, and by this line it could be seen how deep it must be to answer its purpose. In order to obtain the level, and at the same time to employ a great many hands, shafts were sunk along the whole line at a distance of less than a hundred feet from one another. It was easy to calculate how deep each shaft ought to be, so as to bring the bottom of the tunnel to the level which it was intended to give to it. These numerous shafts also facilitated the running off of the water on account of the pressure of the air, and at the same time rendered access to the tunnel easy. On any other plan only few persons could have been employed at a time, whereas now from every shaft two parties worked in opposite directions and broke through the rock. This working of different parties towards one another also insured their keeping the exact level. This tunnel, which was the admiration even of ancient Rome, has now existed for a period of 2500 years; it is still entire, and will exist in all time to come, unless some great revolution of the earth shall break it to pieces. The Roman cloacae are of the same character, and will endure until the last day of the earth. There are many such tunnels in the Roman territory, of which at present the advantages alone are perceptible, but whence they carry the waters can no longer be ascertained. Such is the case near lake Nemi: the whole valley of Aricia was formerly a lake, which is now perfectly drained. There, too, a great thing was effected by a little tunnel: the valley of Aricia is one of the most fertile in the world, and is still the same as it is described by Pliny. The fertility in Italy is so great that wheat, unless it is weeded, cannot grow; agriculture there requires a degree of industry of which we have no idea; if any one were to introduce there the system of Flemish or English agriculture, it would lead to ruin. The _Vallis Albana_ is the modern valley of Grotta Ferrata. In the east of Latium, in its narrower sense, we have the towns of THE HERNICANS.