The Benagil Sea Cave is the crown jewel of the Algarve coast and one of the most spectacular natural formations in all of Europe. Carved over millennia by the relentless pounding of Atlantic waves against the golden limestone cliffs, this cathedral-like grotto features a massive domed ceiling with a circular opening at the top, through which sunlight streams down to illuminate a small sandy beach and the turquoise water below. The effect, especially in the morning when the sun is at the right angle, is almost otherworldly, as beams of light create shifting patterns on the cave walls and the water glows an impossible shade of blue-green.

The cave is only accessible by water, which adds to its allure and sense of discovery. Most visitors arrive by small boat tour from Benagil Beach, a five-minute ride that also passes several other dramatic sea caves, arches, and rock formations along this stretch of coast. For the more adventurous, kayaking or stand-up paddleboarding to the cave allows you to actually land on the interior beach and spend time inside, something the larger tour boats cannot do. The surrounding Algarve coastline offers dozens of other spectacular cliff formations, hidden beaches, and sea grottos worth exploring.

Pro tip: Go by kayak rather than tour boat if conditions allow. Boat tours pass through the cave but cannot stop, giving you only a few minutes to photograph the interior. In a kayak, you can beach on the sand inside the cave and soak in the atmosphere at your own pace. Book the earliest morning slot for the softest light and fewest other visitors, and always check sea conditions before heading out.