ALBA´NUS LACUS now called the Lago di Albano, is a remarkable lake of Latium, situated immediately beneath the mountain of the same name (now Monte Cavo), about 14 miles S. E. of Rome. It is of an oval form, about six miles in circumference, and has no natural outlet, being surrounded on all sides by steep or precipitous banks of volcanic tufo, which rise in many parts to a height of three or four hundred feet above the level of the lake. It undoubtedly formed, at a very early period, the crater of a volcano, but this must have ceased to exist long before the historical era. Though situated apparently at the foot of the Mons Albanus, it is at a considerable elevation above the plain of Latium, the level of its waters being 918 feet above the sea: their depth is said to be very great. The most interesting circumstance connected with this lake is the construction of the celebrated emissary or tunnel to carry off its superfluous waters, the formation of which is narrated both by Livy and Dionysius, while the work itself remains at the present day, to confirm the accuracy of their accounts. According to the statement thus transmitted to us, this tunnel was a work of the Romans, undertaken in the year 397 B.C.,and was occasioned by an extraordinary swelling of the lake, the waters of which rose far above their accustomed height, so as even to overflow their lofty banks. The legend, which connected this prodigy and the work itself with the siege of Veii, may be safely dismissed as unhistorical, but there seems no reason for rejecting the date thus assigned to it. (Liv. 5.15-19; Dionys. 12.11-16, Fr. Mai; Cic. de Divin. 1.44.) This remarkable work, which, at the present day, after the lapse of more than 2000 years, continues to serve the purpose for which it was originally designed, is carried under the ridge that forms the western boundary of the lake near Castel Gandolfo, and which rises in this part to a height of 430 feet above the level of the water; its actual length is about 6000 feet; it is 4 feet 6 inches wide, and 6 1/2 feet high at its entrance, but the height rapidly diminishes so as in some places not to exceed 2 feet, and it is, in consequence, impossible to penetrate further than about 130 yards from the opening. The entrance from the lake is through a flat archway, constructed of large blocks of peperino, with a kind of court or quadrilateral space enclosed by massive masonry, and a second archway over the actual opening of the tunnel. But, notwithstanding the simple and solid style of their construction, it may be doubted whether these works are coeval with the emissary itself. The opposite extremity of it is at a spot called le Mole, near Castel Savelli, about a mile from Albano, where the waters that issue from it form a considerable stream, now known as the Rivo Albano, which, after a course of about 15 miles, joins the Tiber near a spot called La Valca. Numerous openings or shafts from above ( spiramina ) were necessarily sunk during the process of construction, some of which remain open to this day. The whole work is cut with the chisel, and is computed to have required a period of not less than ten years for its completion: it is not however, as asserted by Niebuhr, cut through lava hard as iron,but through the soft volcanic tufo of which all these hills are composed. (Gell, Topogr. of Rome, p. 22-29; Nibby, Dintorni di Roma, vol. 1. p. 98-105; Westphal, Römische Kampagne, p.25 ;Abeken, Mittel-Italien, p. 178; Niebuhr, vol. ii. pp. 475, 507.) Cicero justly remarks (de Divin. 2.32) that such a work must have been intended not only to carry off the superfluous waters of the lake, but to irrigate the subjacent plain: a purpose which is still in great measure served by the Rivo Albano.The banks of the lake seem to have been in ancient times, as they are now, in great part covered with wood, whence it is called by Livy (Liv. 5.15) lacus in nemore Albano.At a later period, when its western bank became covered with the villas of wealthy Romans, numerous edifices were erected on its immediate shores, among which the remains of two grottoes or Nymphaeaare conspicuous. One of these, immediately adjoining the entrance of the emissary, was probably connected with the villa of Domitian. Other vestiges of ancient buildings are visible below the surface of the water, and this circumstance has probably given rise to the tradition common both in ancient and modern times of the submersion of a previously existing city. (Dionys. 1.71; Niebuhr, vol. 1. p. 200, with note by the translators.)
[E.H.B]