On my way to Bologna and Firenze I stayed for three days in Milan. I visited the Duomo of Milan which is one of the biggest Cathedrals of the world. The Cathedral hosts the Duomo Sundial which was built in 1786 by the astronomers of Brera. The Sundial or Meridian Line measures theoretical 61,53m (horizontaly 55,07m and due to be blocked by the northern church's wall the meridian line ends vertical by 2,5m height).
The sun light, is entering through a 25,2mm pinhole located at 23,8188m height in the church's ceiling. Due to the construction of the roof, the sun light only enteres the pinhole a 15min before and after it's heighest point in the sky.
Some interesting math about this Duomo Meridian line can be found via this website.
Other interesting data about the Duome Meridian line is available aswell via :
