In 2000, an underground nymphaeum was discovered in the cellars of the convent of the Benedictine Mothers of St. Catherine, situated in the historic centre of Teano. The nymphaeum was probably part of the domus identified below the Loggione, which today houses the museum. It had a rectangular plan, the long axis on a more or less east/west alignment, with an apse in the east side and a barrel vaulted roof. The dimensions were: length 5.80 m; width 6.40 m; diameter of the apse 3.80 m; height circa 5 m. It was built in opus reticulatum with tufa block quoining. The walls were animated by semi-pilasters and alternating semicircular and rectangular niches and were completely faced with artificial stalactites, still well preserved, made of Roccamonfina lava imitating a rocaille. A thin sheet of water must have flowed over it, as attested by the numerous fistulae visible both on the walls and inside the niches. The decoration was completed by an frieze of encrusted elements, which ran along the top of the walls, and columns with marble bases, all elements which unfortunately had been robbed.

The buildings chronology can be placed in the period of transition from the 1st century B.C. to the 1st century A.D., with probable restorations being undertaken between the 2nd-3rd century A.D.