ALETRIUM (mod. Alatri)  , a town of the Hernici, about 6 m. due N. of Frusino, Italy, mentioned in 306 B.C. for its fidelity to Rome . In Cicero's time it was a municipium, and continued in this position throughout the imperial period . It is chiefly remarkable for its finely preserved fortifications constructed of tetrahedral and polygonal blocks of local limestone well jointed, with maximum dimensions of about 3 by 1 ft.; the outer circuit of the city wall measures about 2 m . It is almost entirely an embanking wall, as is the rule in the cities of this part of Italy, with a maximum height, probably, of about 30 ft . Two of the gates (of which there were perhaps five) are still to some extent preserved, and three posterns are to be found . In the centre of the city rises a hill (1647 ft.) which was adopted as the citadel . Remains of the fortifications of three successive periods can be traced, of'which the last, perhaps a little more recent than that of the city wall, is the best preserved . In the first two periods the construction is rough, while in the third the blocks are very well and finely jointed, and the faces smoothed; they are mostly polygonal in form and are much larger (the maximum about ro by 6 ft.) than those of the city wall . A flat surface was formed partly by smoothing off the rock and partly by the erection of huge terrace walls which rise to a height of over 50 ft., enclosing a roughly rectangular area of 235 by 115 yds . Two approaches to the citadel were constructed, both passing through the wall; the openings of both are rectangular . The architrave of the larger, known as Porta di Civita, measures about 17 ft. in length, 5 ft. in height, 6 ft. in thickness; while that of the smaller is decorated with three phalli in relief . Later, though probably in ancient times, a ramp was added on the northern side .

In the centre of the arx was a

building on the site of the present cathedral, of which only a small portion is preserved . Remains of a high-pressure aqueduct, which supplied the town with water and was constructed with other public buildings (Corp . Inscr . Lat. x., Berlin, 1883, p . 5807) by L . Betilienus Varus, may still be traced . A temple was excavated in 1889 about :1m. to the north of the town, and many fragments of the painted terra-cottas with which it was decorated were found . A reconstruction of it has been erected in the Museo di Villa Giulia at Rome . The present town (pop. in 1Q01, 15,322) has a picturesque aspect, and contains many buildings in the Gothic style . See R . Bassel, Centralblatt der Bauverwaltung, 1881, I21, p . 134; H .

Winnefeld, Ramische Mitteilungen, 1889, 126; G . Fiorelli in Notizie degli Scavi, 1882, 417 . (T .