The most densely populated is Castelromano which is positioned in a plain at the base of the La Romana mount, elevation 862 metres (2,828 ft), 5 kilometres (3 mi) from Isernia.

[5] After the complete subjugation of the Samnites, a colony, with Latin rights (colonia Latina) was settled there by the Romans in 264 BC the city, a key communication center between southern Italy and the inner Appennine Regions.

[6] During the Social War it adhered to the Roman cause, and was gallantly defended against the Samnite general Vettius Scato, by Marcus Claudius Marcellus, nor was it till after a long protracted siege that it was compelled by famine to surrender, 90 BC.

Henceforth it continued in the hands of the confederates; and at a later period of the contest afforded a shelter to the Samnite leader, Gaius Papius Mutilus, after his defeat by Lucius Cornelius Sulla.

[citation needed] In the following weeks they came back twelve times without ever hitting their targets: the bridges of Isernia, Cardarelli and Santo Spirito, then built entirely of iron, towards the internal area.

[10] The coins of Aesernia, which are found only in copper, and have the legend "AISERNINO", belong to the period of the first Roman colony; the style of their execution attests the influence of the neighboring Campania.

The famous Fraterna Fountain, the town's main symbol, was built in the 13th century: it is made up of living stone's slabs coming from ruined Roman monuments, while all the rest is a work of local masters, commissioned by the Rampini family of Isernia.

The higher fillet presents a line of smooth ashlars on which twelve little hanging arches set, supported by little brackets adorned with zoomorphic, phytomorphic and geometric motives.

On the bottom of the fountain, on a second level in respect to the arcade, you can distinguish two blocks of Roman age with some swags and a funerary epigraph dedicated to the god Mani.

A deep study of the surfaces allows to verify that the blocks were worked on several occasions, with an extremely long interval, and that come from an undefined number of buildings of the town.