The building of Roccabruna is in an isolated area and it is one of the most unique buildings in the Villa.
It is reached with a path visible on the right just before the Antiquarium, walking along an ancient olive grove.
The name Roccabruna probably is due to the fact that inside it was completely blackened by the smoke of the fires that were lit there by the shepherds; even in the 1980s, before the restoration, a flock of goats was in the shade and cool inside the large circular room on the lower floor.
Today only the lower floor of Roccabruna remains, a massive quadrangular cube with three-meter thick perimeter walls; the main door gives access to a large circular Hall, nine meters in diameter, which has four rectangular niches on the main axes and four apsidal niches on the diagonals.
The walls of the great Hall were once covered with precious marbles, but only the holes of the clamps that held them in place remain. The floor was also made of marble, opus sectile with concentric rows of triangles, but only the imprints are left. Its blind dome was plastered, according to some scholars it seems that it was covered with mosaic decorated with stars, but nothing remains.
In the dome there are three slits coming from masonry conduits that emerge on the three outer facades: they had a very specific function, that we discovered thanks to Archaeoastronomy.
There are a few rooms around the Hall, much remodeled by the Jesuits in the eighteenth century, when they built staircases and several chapels, one of which was unknowingly created in a latrine.
On one side of the building is a long inclined ramp supported by arches that goes up to the Accademia Esplanade: it was its main access. Further on, a large staircase gave access to a Temple that no longer exists: there are only fragments of marble and masonry scattered all around. Originally the Temple was circular with sixteen Doric columns, but the inner cell was octagonal and had three windows.
The staircase leading to the temple still exists and leads to a magnificent panoramic terrace from which on clear days the dome of St. Peter's can be seen. This means that at the time of Hadrian it was possible to see his Mausoleum, today's Castel Sant'Angelo.
To the south-east the sanctuary of Fortuna Primigenia of Palestrina was seen, and also today.The entrance door of the Temple faced the building of the Accademia, which today is no longer visible because in the Accademia Esplanade there is an extensive olive grove.
The columns of the Temple rested on the perimeter walls, three meters thick, so as not to weigh on the dome of the lower floor; therefore Roccabruna had two domes one on top of the other, a true architectural acrobatics.
Above the main door of the circular Hall in the lower floor there is a "light conduit" chat creates extraordinary illuminations (hierophanies), only during the days of the Summer Solstice (June 21st). At sunset the rays of the Sun create a Blade of Light inside the dome of the lower floor, which is visible for more than an hour and moves with an arched path, turns red and then goes out, as seen in the video.
The Sun sets in the center of the main door of the circular Hall and illuminates the niche on the opposite side, where probably was a statue of the goddess Isis; a candelabrum base with the symbols of the goddess including the sistrum, the torch and the asps was found in the building.
The symbolic meaning of this illumination and of the e Accademia Esplanade is explained in detail in our book «Villa Adriana. Architettura Celeste. I segreti dei Solstizi», published by Rirella editrice.
The Accademia Esplanade was the true Acropolis of the Villa, closer to the divinity, part of a Sacred Landscape; Roccabruna was probably dedicated to the goddess Isis.