Unnamed Road, Milos 848 00, Greece
Kleftiko BeachLocals claim there are 75 beaches on volcanic Milos, ranging from brilliant white to black, red, and gray. Hidden fjords, hot springs, and underwater caves make a stunning setting for kayaking, scuba diving, and sailing. The otherworldly coastline is also a refuge for monk seals. If you’re lucky, you might spot some as you swim through Kleftiko, a series of white rock formations eroded by the piercingly blue sea. Pirates used to lurk in the caves, waiting to capsize ships. A round-the-island boat trip includes a swim through Sikia Cave, where sunbeams bounce off the cobalt water and mineral deposits cause rainbows to ripple across the rocks.