A large post 7th century A.D. cistern came to light during the restructuring, undertaken by the Superintendency, of the east wing of the monumental complex of SS. Severino e Sossio, home of the Naples State Archive. This large structure (circa 2.80 × 8.50 m) may have belonged to the monastery that was built as early as the end of the 9th century, together with a small Benedictine church. From the following century onwards, the monastery began to enlarge and soon became one of the main centres of the monastic order in Naples. The excavation revealed the sequence of restoration and patching carried out on the cistern until its final obliteration. This was caused by the construction of a lime kiln that was probably used during the building of the so-called “chiostro dei marmi” of the monastery of SS. Severino e Sossio, that was completed at the end of the 16th century.