The largest calanque hit headlines in 1991 when diver Henri Cosquer from Cassis swam through a 150m-long passage 36m underwater into a cave to find its interior adorned with wall paintings dating from around 20,000 BC. Now named Grotte Cosquer , the cave is a protected historical monument and closed to the public. Many more are believed to exist.
Take bus 23 from Marseilles' Rond-Point du Prado metro to La Cayolle stop, from where it is a 3km walk.
Two seasonal restaurants with fabulous views serve lunch (and require reservations). Le Château has the best food but does not take credit cards; Le Lunch (which also serves dinner) has the better view. Diners with reservations are allowed to drive into the calanque ; otherwise, mid-April to May the road's open to cars weekdays only and closed entirely June to September.
