Santorini is one of the most famous and beautiful places I've ever been, and there was so much to do and see that I was overwhelmed trying to do as much as I possibly could. But since most of us don't have an infinite amount of time to spend on this picturesque island, here's the top five things you need to do when you're here.
Oia is the most famous spot on the island, for good reason. This village, with its windmills, pedestrian streets, and blue-domed churches, clinging to the cliffs has the best views on the island, especially at sunset. When you're here, make sure you see the ruins of Oia Castle for a 360-degree view of the the town, the whole Western side of the island, and the caldera. You should also walk down to Amoudi Bay, where you should splurge on a drink or a meal at one of the iconic seaside restaurants.
The hike from Fira to Oia (or Oia to Fira!) takes you along the rim of the caldera through the picturesque villages of Firostefani and Imerovigli. Almost every step of the two to three hour hike gives you incredible views. The route is well-marked and well-traveled, but it's not meant for strollers or bikes. You also don't want to use Google Maps to route this walk because it'll take you a more direct route off the trail and you'll miss some of the best views.
As beautiful as the views from Santorini are, I think the views of the island from the water are just as stunning. If you're visiting Santorini as part of a cruise, then you're already going to get those looking-up-at-the-island views, but if you're staying on the island, there's lots of sailing options - yacht tours, private tours, group tours, etc. Pick whichever tour suits your budget and preference - some boats go to different beaches, some to hot springs, etc. - but whatever tour you choose make sure you're out on the water at sunset.
Santorini is famous for its vineyards and produce because of the rich volcanic soil found all over the island, and no trip to Greece would be complete without a food tour. So, find a tour that suits you - do you want a wine or beer (or both!) tasting? Do you want your food tour to double as a walking tour of one of the towns? etc.
Skaros Rock is a large rock formation on a peninsula near the town of Imerovigli. This rock was once home to a castle that protected the island from pirates, and you can still see ruins of the castle today. It takes about an hour (round trip) to walk to and from Skaros Rock from Imerovigli, but that's not including any exploring you do on and around the rock once you get there. You can detour to Skaros Rock from the Fira to Oia hiking trail, or you can make Skaros Rock its own excursion.