The Benedictine Abbey of the Holy Trinity stands like a silent guardian of time, immersed in the green Selano Valley. Founded in the 11th century by St. Alferio, the abbey was born in the silence of the cave of Arsicia, where the saint withdrew to live in prayer. The humble refuge soon became a beacon of spirituality and culture. The interior of the Basilica is revealed in all its harmonious beauty. The soft light enhances the richness of the polychrome marble that covers the surfaces, enveloping the visitor in an atmosphere of peace and contemplation. Among the artistic marvels housed in the Basilica is the precious 12th century Cosmatesque mosaic ambo, donated by King Roger II of Sicily in honor of the resting place of Queen Sibyl, his second wife.

a. Cloister
Surrounded by rocks, the small 14th century cloister is a unique oasis of peace. Its irregular shape, enhanced by elegant arches and twin columns, creates a fascinating play of light and shadow. The Roman wall, still intact in the innermost part of the cave, testifies to the presence of buildings before Alferio's arrival. The small sculpture of a faun, found in a wall that delimited a part of the cave, could be a reference to ancient pagan cults practiced in this vast cave.

b. Longobard Cemetery
Hidden in the basement of the basilica and the cloister is the imposing Lombard cemetery, a place of eternal rest for monks and believers who, between the 11th and 13th centuries, chose to rest in this corner of peace and sanctity. The structures date back to different periods: under the basilica, the foundations of the church of St. Alferio are preserved, with a long corridor divided into three rooms, the first of which is the chapel of St. Germano, dating back to the 13th century. This chapel was decorated with frescoes from the 15th and 16th centuries, including works by Andrea da Salerno, now preserved in the old chapter house. Next to the corridor, a series of gray tuff arches indicate the presence of illustrious tombs, including the sarcophagus of Costanzo Punzi, treasurer of King Robert of Anjou, buried here in 1338. Beneath the small cloister, there are early medieval structures dating from the 9th century, with round masonry pillars, and 13th-century structures connected to the cloister itself. To the west are deep pits covered by vaults, probably part of the oldest cemetery. The whole area was used for burials over the centuries, but recently the bone remains have been exhumed and transferred to an ossuary in the garden, near the monks' cemetery chapel.

c. Library and Archives
The monumental complex houses authentic treasures of European culture. The library and archives preserve medieval manuscripts and illuminated codices, witnesses of knowledge that spans the centuries. Among the most precious relics is the Codex Legum Langobardorum: a collection of Lombard laws and capitulars of the Frankish kings, reflecting an era when justice began to forge the foundations of civilization.