ALETRIUM (mod. ALATRI), a town of the Hernici, about 6m. due N. of Frusino, Italy, mentioned 3o6 B:C. for fidelity to Rome. In Cicero's time it was a municipium, and continued in this position throughout the imperial period. Finely preserved f ortifi cations of blocks of local limestone have an outer circuit of about 21m An embanking wall, the rule in the cities of this part, has a maximum height of about 3of t. Two gates and three posterns are to be found. A central hill (1,647ft.) was the citadel. Forti fications of three periods can be traced; the last, perhaps a little more recent than the city wall, is best preserved. 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 soft., enclosing a roughly rectangular area of 235 by I I Syds. Two approaches to the citadel pass through the wall.