Grey granite and white marble

Mons. Filippo Luigi Gilj, Vatican Astronomer.

1817

Length:

• 70.79 m

St Peter’s Square.

   The St. Peter's Square sundial was built in 1817, under the pontificate of Pius VII ( 1800-1823), by Vatican astronomer Archbishop Filippo Luigi Louis Gilj. The entire work was funded by Bishop Pietro Maccarani, Treasurer of St. Peter’s Factory, as noted by an inscription carved on the white base of the obelisk (north side) .
    The sundial is formed by a straight line in gray granite, interspersed with marble discs, from the base of the obelisk, the sundial’s gnomon, and extends to the right-hand colonnade. It allows one to determine local noon.
    Using the position of the shadow of the Cross, located at the top of the obelisk, it is possible to determine the declination of the sun and the seasons. The two marble discs at the ends of the strip indicate the two-day solstice of the year, June 22 and December 22. Between these two extremes five other records indicate the passage of the sun in the twin zodiac signs : Leo - Gemini, Virgo - Taurus, Libra - Aries , Scorpio - Pisces - Aquarius and Sagittarius .
    After 1817 the discs were changed once in 1852 when the first gas chandeliers were placed in the square, and again in 1878 or 1880 at the time of Leo XIII ( 1878-1903), and one last time in 1924

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