The abbey of Casamari is situated in the territory of Veroli (Frosinone), on the Via Maria, mid-way between Frosinone and Sora, and lies on a rocky hill sloping down to the torrent Amaseno, at about 300 metres above sea-level. It was built on the ruins of an ancient Roman municipium named Cereatae, being dedicated to the goddess Ceres, at Marianae, for it was the birthplace, or at least a residence, of Caius Marius, from whom the abbey later derived its name. The documents witness the presence of a Benedectine monastic community in the 11th century, under the name of Casamari.

The monastery soon showed a strong vitality both spiritual as well as social and economical, but, in the early 12th century it was affected by a rather long crisis due to a sort of ungovernability (which is witnessed by the frequent resignation of its abbots) caused by both a decline of the Curtis system and the political and religious confusion of that period. During the schism of Anaclet II (1130-1138), when Bernard of Clairvaux, by his persistant work of mediation, became the leading promoter of the Church's unity through the recognition of Innocent II as pope, Italy became acquainted with the Cistercians. She appreciated their spirituality and requested their presence, while all Europe watched and supported the Order's astonishing, miraculous expansion.
It was with that political and religious background that a large number of Benedectine monasteries applied for incorporation to this religious Order which guaranteed absolute faithfulness and the popes themselves promoted an aggregative movement. The abbey of Casamari, too, was incorporated to the Order of Citeaux through Bernard's personal initiative and became the XXIX direct daughter-house of Clairvaux.
The Cistercians started the construction of the monastery which we can still admire today, following the Order's typical planimetry, pulling down some parts of the ancient Benedectine building and using others as a "valetudinarium" (hospital). In 1203, Pope Innocent III blessed the first stone of the church, the construction of which went on under the management of Fra' Guglielmo of Casamari until 1217. On September 15th of that year; the basilica was consecrated and dedicated to Our Lady Received into Heaven, according to the Order's custom, and to the Roman martyrs, John and Paul.
The rise of European States on the fall of the pope's temporal power; the captivity in Avignon (1305-1377) and the great western schism (1378-1417) brought about a general crisis of ecclesiastic institutions which necessarily involved all religious Orders. The Cistercian monasteries, which in the age of Communes had been strong representatives of democratic ideals and of a deep Christian attitude, lost their properties and spiritual prestige.
Casamari suffered heavy damages in the early 15th century when Ladislaus of Anjou, after storming Veroli, besieged and plundered the monastery. ln 1417 the mercenary troops of Muzio Attendolo Sforza, at the service of Queen Joan II of Naples and allied to the pope, attacked the armies of Jacopo di Caldora and the Count of Mondrisio, both supporters of Braccio di Montone, who were barricaded in the monastery. It has been said that the western wing if the building was damaged in the clash.
After the war, the cause of Casamari's decline, and that of other monasteries too, was the institution of the commendam. It was extended to the abbey by Pope Martin V, in 1430, in favour of his nephew Cardinal Prospero Colonna and it was suppressed only in 1850 by Pope Pius IX. In 1623 the community, reduced to eight monks only, joined the Roman Congregation along with eight other abbeys. In 1717 the commendatory Abbot Annibale Albani introduced the reform of La Trappe into the abbey by calling up some monks from Buonsollazzo in Tuscany.
During Napoleon's first campaign in Italy some French soldiers, on their way back, plundered the monastery and desecrated the Eucharist, although they had been received with open arms by Prior Simon Cardon. Some of the monks were able to escape, but six of them, among whom the prior himself, were slain while gathering the sacred particles. They were thus considered martyrs of the Eucharist and later buried in the abbey church. In 1833 the monks of Casamari reacquired the monastery of San Domenico of Sora and, in 1864, Valvisciolo which, in the meantime, had been restored by Pope Pius IX at his own expense. In 1873, owing to the laws of suppression, the abbey was deprived of its possessions and the following year; was declared a national monument.
In spite of endless change, Casamari is still one of the Cistercian monasteries in which monastic life has had no interruptions since its foundation, except for the short period 1811-1814. The revival of religious life has been made possible by the institution of seminaries (1916) which have in a short time set many young men on the way to the Cistercian ideal. Thus the abbey, together with its dependent houses, was declared a monastic Congregation by the Holy See in 1929. Its Constitutions were approved provisionally in the same year and permanently on June 13th, 1943 by Pope Pius XII. They were approved again in 1979, after a revision according to the instructions of Vatican II. The general Chapter meets every three years. The abbot of Casamari is always the Abbot President ofthe Congregation and is in office for a nine-year period. Owing in part to the influence of the Trappists' severe observance in the 18th-19th centuries, common prayer; above all liturgy and lectio divina, is very important to the Congregation's spirituality. They spend a large part of their time in work, by which they earn a living for themselves and some aid for the poor and missions. Their occupations vary from teaching to sacred ministry as well as scientific, handicraft and agricultural works. In 1830 the Congregation, entrusted by the Holy See, introduced the Catholic monasticism into Ethiopia and started the education of the first group of Ethiopian postulants. In 1940 the first monastery was founded, and there are now four monasteries and two missions with almost 100 monks. In the meantime, from the mother-house, Casamari, have come other groups of monks, giving life to some new monasteries, one of which is in the United States of America and another in Brazil. According to the latest statistics, the Congregation of Casamari now consists of sixteen monasteries and three residences, with 220 monks.

The carthusian monastery of Trisulti

Monastic life was started at Trisulti, situated at the foot of Mt. Rotonario, in the territory of Collepardo, diocese of Alatri, by St.Dominic of Foligno, a great reformer and founder of Benedictine abbeys in southern Latium. In the year 1000, he built a magnificent monastery, which we can still admire, despite the collapse of the central part (the church and chapterhouse). After two centuries of Benedictine life, Pope Innocent III decreed in 1204 that the abbey and its possessions should pass to the Carthusians, who sent four laybrothers with the task of building a new monastery suitable for their kind of monastic life and safe from rockfalls.
The construction of the charterhouse was carried out very close to the old abbey. The official installation took place on September 25th, 1208, with monks coming from the charterhouse of Casotto. On July 17th, 1211, the new church was consecrated and dedicated to the apostle St. Bartholomew, again by Pope Innocent III, who, as a sign of his benevolence towards the monks, had a palace built for himself in the surroundings. This building was restored in 1958 and is still called by his name. A number of changes in the course of time have masked the charterhouse's original appearance. Since 1947 the monastery has been inhabited and looked after by the Cistercians of Casamari who carry on a holy witness by their life interwoven with work and prayer. The small group of monks, a simple priory directly dependent on the abbey of Casamari, gave life to the old charterhouse, welcoming tourists and, above all, offering their services to parish priests in the neighbourhood.