Alba Longa

Note: this is the least serious research I have done (we neeed archaeological proofs…), but I love it and I’m still convinced that the idea of a Bronze-age natural sundial makes sense, it’s there under our eyes.



Hypothesis on the location of Alba Longa on the western crater rim of the Albano Lake,
based upon the observed light belt cast there soon after sunrise.
(published in: “Archeologia w teorii i w praktyce”, Warszawa – Poland , 2000).

In Italian:
(published in: “Documenta Albana”, II serie n. 21 – 1999 – Museo Civico Albano, pp. 25-42).

According to tradition, Alba Longa is the Latin town, founded in the XIIth century BC, from where, four centuries later, originated the foundation of Rome. It was destroyed in the VIIth century BC. In classical literature it is said to stretch out along a ridge at the base of Mount Albano, the religious centre of the Latin people dedicated to Jupiter, associated with the modern Monte Cavo. Until today the location of Alba Longa has never been established with certainty.
In this publication, the hypothesis is forwarded that the well-marked light belt, cast at sunrise upon the western rim of the Albano crater, might explain the name of Alba Longa as “sunlit ridge” (“sunlit” for alba, white), and therefore eventually confirm its location there. This hypothesis is based first upon field observations and then upon the results of three-dimensional dynamic modelling of the landscape- and solar data of the area around the Vulcano Laziale, south-east of Rome.
Although  the  whole western rim of  the Albano crater is involved in the observed light pattern, the  present town  of Castel Gandolfo is proposed as the central place of the phenomenon. The particular morphological features of the volcano allow potentially the sun’s yearly evolution and crucial dates to be well observable from the western rim of the Albano crater and from Monte Cavo.
In the model the solar data of 1000 BC were used, a proxy for the foundation date of Alba Longa. However, the small differences in the sun’s azimuth angles between the past and the present, as well as the practically unchanged morphology of the volcano, render the “sunlit ridge” and the shadow cast by the Mount Albano (the “natural sundial”), so well visible today as it must have been 3000 years ago.

Scheme of the proposed natural sundial over the western rim of the Albano lake.
Alba Longa WP_summer
Modeled aerial view of “Alba Longa” during summer solstice; at this time of the year the early morning sunlit belt is wel defined; this phenomenon lasts for about 2 months.
Modeled aerial view of “Alba Longa” during winter solstice; also in this time of the year the well-defined morning sunlit belt casts over Castel Gandolfo, for a duration of about 2 months.




In the other times of the year, i.e. the periods around the equinox, each about 2 months long (if we take into account transition periods) and with a slight shift towards the summer solstice, the natural sundial changes it’s form from a sunlit belt into the pointed shadow of Monte Cavo (Mount Albano), cast in the early morning over the western rim of the Albano lake.

Modeled situation during equinox: well visible is the pointed shadow of the Monte Cavo cast to the north of Castel Gandolfo.

Between halfway summer solstice and autumn equinox, the morning shadow cast by the Monte Cavo is moving slowly from left to right, i.e. from S to N (see sundial scheme).

Halfway between summer solstice and autumn equinox: the midsummer morning shadow cast by the Monte Cavo (Mount Albano) over the “Albalonga” rim, the 12th of august 2012, 7.44 h. legal time, between Domitianus’ villa (to the left) and Castel Gandolfo (ARROW; to the right).
The natural sundial during autum equinox 2012: the shadow of the Monte Cavo retracts from the western ridge of the Albano crater, between the hills of Castel Gandolfo (ARROW; lefthand) and Monte Cucco / Monte Crescenzio (righthand); in the background the Tyrrhenian sea.

Between autumn equinox and winter solstice, the morning shadow is moving still further from S to N, reaching the town of Marino.

30th of October 2012, 8.00 h. solar time: the early morning is cast over Marino (ARROW); to the extreme left the Albano lake.
Winter solstice 2014: to the right the shadow of Monte Cavo over Rome, to the left the town of Marino, just lighted by the sun…



During the equinox period the sun rises close to the top of the Mount Albano, when seen from Castel Gandolfo and the area to the west of it. In the same period, the full moon rises as well in that position. To be remarked that full moons always rise in the same position as the sun, considering that sun and moon are then opposite to each other. But only during the equinox period the sun and the full moon rise close to Mount Albano when seen from Castel Gandolfo.

Sunrise over Monte Cavo (Mount Albano) and the lake during the equinox-period, as seen from Castel Gandolfo, the 17th of september 2008, about 7h.23 legal time (photograph Caroline Lawrence).
Full-moon rise over the Monte Cavo (Mount Albano) and the lake during the equinox-period, as seen from Castel Gandolfo, the 16th of september 2008 (photograph Caroline Lawrence); the illuminated village is Rocca di Papa; actually full moon was on the 15th of september 2008, so here we are one day on the way to last quarter.
Winter solstice sunrise seen from Castel Gandolfo: the Albano lake, between Monte Cavo (Mount Albano, to the left) and the Capuccini hill (to the right), the 21th of december 2008, 7h.53, direction towards east. For more photographs see Facebook album My Alba Longa.
Digital model of the sunrise during summer solstice as seen from a position to the west of Castel Gandolfo; Monte Cavo (Mount Albano) is the relief to the right.

See also the article on the Nemi  lake.

See also Caroline Lawrence‘s blogspot on a day around Albano lake, the 17th of september 2008.


Earth Sciences for Archaeology