The sundial of the Cathedral of Palermo, designed by the astronomer Giuseppe Piazzi in 1801, is an ancient camera obscura sundial that crosses the central nave. It is more than 21 meters long and uses a small hole in the dome, called a gnomon, to project the sun's ray onto the axis of the sundial, marking midday and indicating the zodiac signs corresponding to the time of year.

canon 7d, Sigma 50mm, f/8, 1 sec, iso 100