In 1848 a sundial was built in the floor of the Auditorium to indicate local midday: every day at midday, a ray of sun passing through a hole in the wall fell on a line on the floor, bordered by marble slabs inscribed with celestial coordinates and astronomical symbols. In 1966 the hole was obstructed by a new building but the sundial was reactivated in 2002 with an electronic device and artificial light simulating the movement of the sun.
