The origins of Spigno are very ancient; after the collapse of the Roman Empire part of the inhabitants survived the frequent barbarian invasions, from the flat towns of the Valle dell'Ausente, took refuge to the north, at the foot of the nearby mountains, where they gave life to a village called "Casalis spinel, by virtue of the thorny shrubs used to protect the fences of domestic livestock.

However, the danger of raiders along the Tyrrhenian coast led the inhabitants of the Casale to move to higher and less easily accessible places where, in Norman times (mid-eleventh century) built the "Castrum spinei"the fortress known in the Middle Ages as the Castle of Spigno, the name by which was indicated the entire medieval village developed along the outer door of the first walls. It was part of the County of Fondi and Tratto for centuries but, with the advent of the French Revolution and the abolition of feudalism (1806) it had its own municipality or municipality.

Spigno has acquired the name "Saturnia" by royal decree of 22 January 1863; the small town of southern Lazio, with just under three thousand inhabitants, covers 38.68 square kilometers and is an integral part of the Park Authority and the XVII Community of Aurunci Mountains. The village is divided into two agglomerations: the first Spigno Superiore or Vecchio, located at the foot of Mount Petrella, preserves the ruins of the ancient castrum and two medieval churches, that of Santa Croce, which has lost its original features following two restorations, the first in the eighteenth century and the second after the last war, and the church of S. Lorenzo al Castello, currently completely ruined. The other agglomeration called Spigno Nuovo, developed in the valley of the Ausente after the last world war, following the destruction of the ancient village. Next to the town hall stands the parish church, dedicated to St. John the Baptist, built in memory of the church that once stood in the ancient town, and of which remains only in the name of the main square.

For centuries the social life of the country, based essentially on an agricultural-pastoral economy, drew fruit from crafts, mainly exploiting the processing of wood for domestic use (still today a town in the country is called, in fact, via Mannesi), the production of coal, and the sale of snow, whose profit in 1690, with forty ducats, constituted the most conspicuous income of the treasury, equal to more than a third of the total. The centuries-old, strong anthropization of the territory offers us the opportunity to rediscover it, following some paths now in disuse. Among these very significant is the sheep track of Ciaia, but no less important is that of Scala Santa, Fontana, and Faito, which leads to the snow ditches and from there to Monte Petrella (1533 m.), Fossa Joanna and the Valley.

The Ciaia sheep track (used until the Second World War to go to the old mill for the milling of cereals) begins at the Conca (Aoseglio), recently called Oasi del Casale, a place where you can still see the ruins of the ancient village. From the Casale, following the hairpin bends of the suggestive path with stone steps, after a few hundred meters on a steep climb, you reach the church of Santa Maria della Misericordia, of which only a few ruins remain. As you climb towards the Castle, the path appears more and more suggestive, offering the visitor the enchanting panorama of the Valle dell'Ausente, in Roman times crossed by the well-known Via Ercolanea that connected the Via Appia to the Latina. The route also allows you to notice, walking, the presence of aromatic plants such as rue, thyme, sage, to which the peasant tradition attributed effective healing properties. The castle is now close and can be accessed from the Portella of the medieval village. The ruins of the ancient fortress are still perched on the rock, are the remains of the Norman walls, still equipped with some side bastions, and inside the crypt of the church of S. Lorenzo, with traces of valuable frescoes.

The Capodacqua spring, located at the foot of Mount Petrella (m1533) has been known since Roman times. The emperor Vespasian in 72 A.D. built an aqueduct 11 km long, which collected the waters of the spring to provide the city of Minturno. After the fall of the Roman Empire, the aqueduct fell into disrepair, and of the imposing construction, for which more than 1000 slaves were employed, only a few leftovers remained. The spring fed for many years the mill and the paper mill of the barons of Fondi and Tratto. The current aqueduct Capodacqua has a capacity of 2500 liters per second and feeds the entire coastal strip with the municipalities of Gaeta, Formia and Minturno, as well as the nearest area within the villages of Castelforte, Saints Cosma and Damiano and Spigno Saturnia.