Cassis is definitely a hidden gem in the South of France (or it was to me, anyways!) I fell so madly in love with the little town, and above all, the Calanques that are in the area. We visited the Calanques both from above & below, which I highly recommend, because it is such a different experience both ways.
After having lunch in the town, we decided to head out on a boat trip to actually get a chance to swim in the Mediterranean Sea, so we headed out from the harbour, and visited both the Calanque Port Pin & The Calanque d'en Vau - And seriously, coming up into them felt like a moment from the Pirates of the Carribean movie - the water was such an amazing turquoise blue colour, and the rock formations were breathtaking. It felt so good to dive into the amazing water and take a dip in such an amazing location!
The next day we hiked to through the Calanques National Park to get a top view (You can hike down from the top to the beaches - it takes about 1.5 hours to do the hike, but that is the only way you can get to the beach, they don't let any boats in, so it is a pretty amazing spot for a beach day!) And the views were just so spectacular! The Calanque d'en Veu was definitely my favourite, I highly recommend visiting it if you are in the area (you can also access it from Marsaille if you don't go into Cassis)
It was definitely one of my favourite places to visit, I can't wait to go back again sometime soon.