The Line of the Sun
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The solstitial gnomon in the Baptistery

The Baptistery of San Giovanni is one of the most ancient astronomical sites in the city of Florence . Already around the year One Thousand, an inlaid marble plaque representing the zodiacal circle was placed near the North door. According to the testimony of Giovanni Villani (14th century) based on "ancient remembrance", the center of the zodiac was struck by light only on the day of the summer solstice (June 21), when a sunbeam entered, at midday, through the oculus in the dome, which was at the time completely open as in the Pantheon. Later, a lantern was built over the dome and the marble zodiac was moved to the eastern side of the building when new flooring was installed in the 13th century, resulting in the "dismantling" of this first extraordinary astronomical monument. A marble zodiac of similar appearance was also placed in the Church of San Miniato al Monte, but it seems to have had no gnomonic function.


2007 IMSS Piazza dei Giudici 1 50122 Florence ITALY