At the end of the first millennium, raids by the Visigoths, the Lombards,
the Saracens and the Ungari had made it difficult to stay in the plains,
where previously many settlements had sprung up. The arrival of the
Barbarians brought devastation and destruction everywhere, and
Montattico followed the fate of Atina. In this period the Benedictines
began a settlement at Pesco Mascolino at the foot of Mount Attico in
an area called Plautus on the left bank of the River Melfa. Soon,
however, this was demolished to make room for what was to become
one of the largest Benedictine monasteries in the Val di Comino at
San Nazario. It was built on the ruins of a temple or a Roman tomb, and was situated on the banks of the River Melfa. There is no certain date for its construction but it certainly dates from before 1000 AD. Most likely it too was destroyed by the fury first of the Saracens and then of the Ungari.
Post 1000AD, the area was part of a feudal system. From this point on in the Val Di Comino, the area was ruled sometimes simultaneously and sometimes alternately by the Princes of Capua, the Counts of Marsi (Marsica), the Abbots of Monte Cassino and the Church, the Counts of Aquino, and the Boncompagni etc.
Around the year 1000AD, during the rule of the Counts of Marsi and following a policy of fortification of villages, work started on a tower at Montattico on the ruins of property once belonging to Titus Pomponius Atticus; this tower was used to watch over the whole valley. Around it rose the village we know today as Montattico. Meanwhile the Princes of Capua, Pandolfo IV and Pandolfo V, handed over the San Nazario settlement to the Benedictines of Monte Cassino, allowing them to build a mill on the River Melfa, with other buildings as required. This windmill is still intact and has become a museum today.
The first confirmed evidence of Casalattico being named thus is from a document dated 1305, now stored in the archives of the Bishop of Sora. It talks of the nomination of Dominus Petrus Andrea as priest of the Church of San Barbato in Casale Attico.
On 9th September 1349 an earthquake devastated the entire valley. During this particular period, lookout towers and fortified walls were built in Casalattico and these have now been incorporated into more modern constructions. In fact, there is still a bell tower at the centre of town and the remains of half a tower that looks out towards Casalvieri. On completion of the fortification work, the Comino Valley became more secure and peaceful. The entire territory was able to flourish as agricultural activities sprung up everywhere and the Church strengthened and expanded with donations especially from the local nobility.
By the early 1600s, the Monastery of San Nazario was completely abandoned and in time was probably demolished by locals who used the remains to build new houses.