Astronomic Orientation at Villa Adriana
bi Giuseppe Veneziano

After the first pictures shot by Marina De Franceschini in june 2006 in the Accademia, in the so called Temple of Apollo, where a wall panel in the lower floor was illuminated by the light of the Sun shining through a window of the upper floor, we started our studies from the orientation given by Vittorio Castellani1. Thanks also to the discoveries of the american architects Robert Mangurian and Mary-Ann Ray, who first saw the light phenomena occurring in Roccabruna during the Summer Solstice, we understood that the Accademia Esplanade and its buildings all had an astronomical orientation.

Therefore we organized several surveys and inspections on the spot, which confirmed that during the Solstices there were very significant light phenomena.

Our coordinated surveys focused on two main buildings: Roccabruna (in the State property) which is at the northern end of the Accademia Esplanade, and the Accademia with the Temple of Apollo (in the Bulgarini private estate).

The two buildings are located ad about 350 m. one from the other, and their geographical coordinates are the following (source: Google Earth):

Roccabruna: 41° 56’ 16,63” North latitude
12° 46’ 23,13” East longitude
100 m. Height above sea level of lower floor
110 m. Height above sea level of upper floor
Tempio di Apollo: 41° 56’ 12,32” North latitude
12° 46’ 39,56” East longitude
114 m. Height above sea level

Then we estimated the ‘real’ rising and setting points of the Sun, as they are visible in these two buildings, during the most significant astronomical events of the year, the two Solstices.

We also estimated the present azimuth of the point where the Sun is rising and setting today, considering the latitude of the two buildings, and we obtained the following results.

During Winter Solstice, the upper part of the Sun is rising at an azimuth of 122° and is setting at an azimuth of 237°; during Summer Solstice, the Sun is rising at an azimuth of 58° and is setting at an azimuth of 302°.

According to the program Planetario 2.0 by Piero Massimino, of the Observatory of Catania (Italy), in year 125 A.D. - the average year of the construction of Villa Adriana - the astronomical Spring Equinox was on march 22nd, Fall Equinox was on september 24th, Summer Solstice on june 23rd and Winter Solstice on december 22nd.

he true inclination of the terrestrial axis on the ecliptic, as we saw before, is not consistent: within a period of about 41.000 years it spans from 22,1° to 24,5°, and this variation is causing a different Sun declination in the sky. Using the Laskar Formula, we estimated which was the Sun declination at that time, and the result is 23°40,5’.

Considering these new parameters we re-estimated the azimuths of the Sun; the out-coming values that we obtained are shown in the following scheme:

Sun Event Azimut in 2010 Azimut in 125 A.D.
Dawn on Winter Solstice 122° 19’ 28 122° 40’36
Sunset on Winter Solstice 237° 40,5’ 237° 19,24’
Dawn on Summer Solstice 57° 40’ 31 58° 10’
Sunset on Summer Solstice 302° 19’ 28 301° 50’

These values have been superimposed on an accurate plan of the Temple of Apollo (AC78) which was measured and astronomically oriented by professor Friedrich Rakob with the german architects Edmund Faller, Dirk Helfgen ed Axel Krück during their surveys between 1991 and 1993.

The azimuths of some structures of this building showed a surprising coincidence with the azimuths of the Sun. And - most of all - we noticed that during dawn of Winter Solstice the rays of the Sun are penetrating through a series of rooms aligned along a longitudinal main axis, which is passing through the geometric center of the temple of Apollo; then the light beam goes further on, passing through the north-western door of the Temple and the other rooms aligned on that side. The same phenomenon occurred during Summer Solstice, but the rays of the Sun followed a reversed opposite course, from north-west to south-east.

These two peculiar phenomena were followed (during Winter Solstice) or preceded (during Summer Solstice) by other striking ‘special light effects’, when the Sun, shining through the windows of the upper floor of the temple of Apollo illuminates the panels and the doors of the lower floor, generating a ‘magic’ that has a deep symbolic meaning. Seen from the geometric center of the Temple of Apollo, these wall panels (which were framed by small columns) have a width of about 18°: if we consider that they were reveted by a thick layer of plaster (which is still visible in situ in the lower panels) their angular width could be 15°, which corresponds to the angular distance covered by the Sun within an hour; therefore the rays of the Sun could move from one panel to the other on every hour.

Similar light phenomena were visible during the two Solstices in the building of Roccabruna. The lower floor was oriented towards the sunset of Summer Solstice and the upper floor - where just the level of the pavement is preserved - was oriented towards the dawn of Winter Solstice.

It is obvious that the present study in not final, since there is so much more to study and to understand. For example, using 3D models it will be possible to understand the light phenomena occurring the Temple of Apollo during Winter Solstice, since the part of the building which has collapsed is the one that was illuminated by the Sun in that period.

As far as Roccabruna is concerned, the present study pointed out that its lower floor is oriented towards the sunset of Summer Solstice. We have to study more thoroughly the orientation of the Temple that once was on the upper floor, oriented towards the dawn of Winter Solstice; there also were other light phenomena created by the central oculus of its dome.

This is just the beginning, because other buildings of Villa Adriana could have been astronomically oriented; to understand if this idea is true, is will be necessary a long research work, that could last for years - if not decades. This is why we decided to publish the results of this preliminary study - focused on these two buildings; we are certain that this will open a new path towards new discoveries with other studies, also for other scholars.


1 Castellani, 2006.