Mediterranean Archaeology and Archaeometry, Vol. 16, No 4,(2016), pp. 473-480 Copyright © 2016 MAA Open Access. Printed in Greece. All rights reserved. 10.5281/zenodo.220972 ASTRONOMY AND SOLAR SYMBOLOGY IN THE BASILICA OF SAN MINIATO AL MONTE AND IN THE BAPTISTERY OF SAN GIOVANNI IN FLORENCE Simone Bartolini 1 , Marco Pierozzi 2 1 Italian Military Geographic Institute (Florence) 2 Italian Navy Hydrographic Institute (Genova) Received: 21/01/2016 Accepted: 23/03/2016 Corresponding author: Simone Bartolini (simo.bartolini@tiscali.it) ABSTRACT The Basilica of San Miniato al Monte is one of the oldest churches in Florence: its construction began in 1018 by the Bishop Hildebrand who wanted to celebrate St. Minias, the patron Saint of the city. The Basilica is one of the finest examples of Romanesque in Tuscany and presents intriguing astronomical and symbolic allu- sions that, however, largely remain undiscovered. This article presents the study on the relationship be- tween architecture, religious symbols and astronomical elements of the church of San Miniato al Monte. In order to identify possible correlations between the position of the Sun and the decorative components of the Basilica that are illuminated by sunlight, we adopted the GNSS methodology and a Total Station. We found that the figures of Christ and the Virgin Mary on the apse mosaic are illuminated by the Sun during the Easter period, and the crypt altar, containing the relics of Saint Minias, is brightened on the day of his martyrdom. The preeminent symbolic/astronomical element is certainly the marble zodiac, similar to that of the Baptist- ery, which Capricorn-Cancer axis coincides with the axis of the Basilica. At the summer solstice a fascinating light phenomenon occurs: the sunlight perfectly illuminates the Cancer sign, thereby confirming the astro- nomical function of the marble zodiac. Furthermore the sunbeams coming from the windows of the right wall of the nave design a path of light on the ideal axis of the Basilica. The re-discovered astronomical role of this zodiac led us to hypothesize that the marble zodiac of the Bap- tistery of Florence was originally placed adjacent to the basement of the columns in front of the northern door of the Baptistery. In this way, on summer solstice day the light beam coming from the central opening of the dome, would have illuminated the Cancer sign, similarly to what happens for the zodiac of San Minia- to. KEYWORDS: San Miniato al Monte, Baptistery of Florence, zodiac, Cancer sign, Capricorn sign, summer solstice, winter solstice, gates of heaven.