Marseille Observatory is an astronomical observatory located in Marseille, France, with a history that goes back to the early 18th century. In its incarnation in 1877, it was the discovery site of a group of galaxies known as Stephan’s Quintet, discovered by its director Édouard Stephan. Marseille Observatory is now run as a joint research unit by Aix-Marseille University and the French National Center for Scientific Research . The old Palais Longchamps facilities are a noted tourist destination in Marseilles area, and a planetarium was also added in 2001. One of the noted exhibits is the Focualt glass-mirror telescope, and various items from centuries of astronomical activities. Focault’s telescope is a noted historical example, because it was the forrunner of the modern style of big reflecting telescopes which use a minute layer of metal on a figured piece of glass. Before this, the main technology was to make the whole mirror of metal, and it would really be another half-century before silvered glass mirrors really caught on for astronomy. A major change in the 20th century was to change from using solution to coat the glass with silver, to use a vapor deposition process.

More details: https://en.wikipedia.org/wiki/Marseille_Observatory