In one corner of the medieval castle in Lanuvio, underlying ancient remains are clearly visible portions of a Roman Theatre of the Augustan age. This came to light in 1831 on the occasion of some construction work.
The bottom wall of the stage, visible for about 8.5 meters, perfectly aligned with the wall of medieval fortification. Among the marble remains are apparent numerous marble fragments including a marble transenna (stone screen) with a winged griffin now kept in the museum (and shown above).
In 1865 two epigraphic fragments were discovered that testify to the attachment of the ancient Lanuvini to this monument that had wanted to restore it at their own expense.