In 2008, a local resident named Salvatore Fosci rediscovered a monumental Etruscan pyramid-shaped altar, just a short distance from the famous Parco dei Mostri (Park of Monsters) in Bomarzo.

The enormous peperino rock was hidden by vegetation on the slopes of a deep canyon and was only discovered for the first time in the 1990s, by two local archaeologists.

The pyramid is believed to be an altar dating back to the 7th or 6th centuries BC, used by the Etruscan haruspices, soothsayers who practiced divination by inspecting the entrails of sacrificed animals. This art of divination was a key element of the Etrusca Disciplina (Etruscan religious scriptures), which had a significant influence on Roman culture.

The altar is positioned toward the northwest, facing the direction of the Etruscan underworld gods (Di inferi). In the heyday of the Etruscan civilization, it must have represented a very important sacred site, though very little is known about it.

Steps and gutters (possibly to facilitate the flow of blood of sacrificed animals) were carved in the altar, which is also known by the name of Sasso del Predicatore (The Preacher's Stone). The steps are steep and holes carved along either side of the steps and on the intermediate levels may have once supported wooden posts and supports.

The area surrounding the pyramid is a treasure trove of Etruscan inscriptions, tombs, medieval ruins, and a mysterious tower associated with the Italian writer and director Pier Paolo Pasolini. Hiking trails connect all of the sites within a four-hour hike.