A multiple sundial can be designed to give the time for different time-zones simultaneously. Examples can be found in the 17th and early 18th century, which were often an extremely complex shape of polyhedral, and even convex, faces.
In some cases, the sundials are formed as hollows in a solid object, e.g., a cylindrical hollow aligned with the Earth's rotational axis or a spherical hollow in the ancient tradition of the hemisphaerium or the antiboreum. In some cases, these multiface dials are small enough to sit on a desk, whereas in others, like here, they are large stone monuments.
Jean-Pierre Jouve (1926 - 2019) (architecte des Monuments Historiques de France)