The building of Roccabruna is a massive quadrangular 'cube' with three meter thick walls; the main door enters a vast circular hall (nine meters in diameter) covered by a dome.
It had a large central niche for a statue, probably that of the goddess Isis, and four smaller apses.
The walls were revetted with in precious marbles, the pavement was in opus sectile with concentric triangles, the dome had a mosaic perhaps decorated with stars.
On one side of the building is
a ramp supported by arches that goes up to the Accademia Esplanade, and reaches a large staircase that gave access to
a circular Temple with sixteen Doric columns that once existed on the upper floor of Roccabruna.
The columns rest on the walls of the lower floor which are three meters thick, so as not to weigh on the dome of the lower floor. Therefore
the building had two superimposed domes, an ‘acrobatic’ architecture.Today in place of the Temple there
is a panoramic terrace from which the dome of the Basilica of St. Peter at Rome can be seen, therefore in Roman times the Mausoleum of Hadrian (the current Castel Sant’Angelo) was visible. Also see the Sanctuary of Fortuna Primigenia of Palestrina was visible from there.
Above the main door of the lower floor there is
a «light conduit» that creates extraordinary illuminations (hierophanies) only on the days of the Summer solstice. At sunset the Sun creates
a Blade of Light inside the dome, which moves in an arc, turns red and then goes off, as seen in the video.
The Sun sets in the center of the main door and illuminates
the niche on the opposite side, where probably was a statue of the goddess Isis . Inside the building a
candelabra base was found with the symbols of the goddess including the sistrum, the torch and the asps.
The symbolic meaning of this illumination and of the Accademia Esplanade is explained in detail in our book «Villa Adriana. Architettura Celeste. I segreti dei Solstizi» published by Rirella Editrice.
It was a Sacred Landscape, the real Acropolis of the Villa.