Tourists visiting Santorini often wonder what there is to explore beyond the beautiful cliff-side towns of Fira and Oia. My advise would be to spend a day or two walking around the towns and spend your lat afternoons at your hotel pool. But, carve out some time and head to Red Beach in the morning, which is located near the ancient site of Akrotíri and is surrounded by impressive red volcanic rock formations. You can get to Red Beach by booking a half day yacht tour via Sunset OIA Cruises or renting a car or 4-wheeler. If you arrive by land, be prepared for a small hike to get there and along the way there is a cute fruit stand where you can hydrate with fresh watermelon (cash only). The beach is full sun and low-key, so bring an oversized umbrella and be prepared to relax (save the partying for Mykonos).
Had I known renting a car would make our journey much easier, I would have took advantage of this option beforehand, however, renting a 4-wheeler and driving it around the cliffs of Santorini worked out just as lovely. You only need a 4 wheeler for one day (40 euros).
If you do rent a car, have it ready upon arrival at the port or airport so you don't have to take an over-crowded bus.