|In the 3rd century, the
emperor Septimius Severus after the dissolution of the Pretorian
army decided to build an encampment near Rome for the soldiers
of the Seconda Legione Partica, at the fifteenth mile of the Via
Appia, so that he could have the soldiers at his disposal, if
necessary. The encampment structure was built utilizing the local
materials, i.e. great peperino blocks.
Among the ruins there is: a large part of the outer wall near
the Convent of San Paolo; the principal Left Gate, i.e. an arch
made of radial ashlars in peperino stone; the majestic Praetorian
Gate on Via Appia, with three barrel vaults. The central one
was very large (6.40 m) to enable wagons passage; the two lateral
barrel vaults were small and only for persons. These had also
two lateral entrances leading to a small space (1.50 m) through
which it was possible to go upstairs; the Cisternoni, the most
interesting and the most impressive among the Castra's monuments.
These five-meter-deep water tanks, dug in the rock, are divided
by five aisles. They are still functioning and can contain more
then 10.000 litres of water. Their plan is almost rectangular
with the two long sides measuring respectively 47.90 and 45.50
metres and the two short sides measuring 29.62 and 31.90 metres.