The calanques are deep narrow inlets, sort of Provencal fiords, in the rocky cliffs along the coast between Cassis and Marseilles. The calanques were formed by rivers flowing into the sea, submerged aeons ago by the rising level of the Mediterranean. The long narrow inlets in the high white rocks are truly impressive, some with tiny harbors or beaches at the ends, and rock climbers scaling the walls along the sides. They've provided safe haven for sailors during storms for millennia, and today the clear blue-green waters are even more popular in good weather.
Boat trips to the calanques are fun to arrange.
Walk along the line of boats at the Cassis harbor and see which ones are filling up for which trips. When you find a boat going to the set you want, that still has good seats available, pay and get in and wait for the departure. Cassis stone has been used around the world, for things as divers as the base of the Statue of Liberty, the Suez canal and the quays of Alexandria. Its durability makes it excellent for lighthouses, and it was used to build the Cassis lighthouse and the 60-meter high Marseilles lighthouse. The white stones growing up out of the sea are partially forested with Pin d'Alep and the scrubby kermes oak .