Portimao

The Benagil Sea Cave near sleepy Carvoeiro is Portugal's geologic equivalent of that one rockstar who's too cool to use the front door. Accessible only via the salty embrace of the Atlantic, your trusty skipper will weave you through cliffs that look like they've endured too many bad breakups, finally slipping into a cavernous dome bathed in sunlight pouring through a hole overhead-nature's own cathedral, complete with a sandy altar. The cave has graced a million Instagram feeds, but nothing beats feeling that quiet, echoing awe (mixed in with some cackling gulls and the purr of boat engines) first-hand. Practical advice: Go early-the mid-morning sun hits the sweet spot, and you'll beat the selfie-stick hordes who arrive later, clogging the waves like tourist cholesterol. Book a couple of days ahead and budget around €25-€35 per person for a quick, breezy cruise; more if your tour includes scenic detours to secret coves where pirates once hid, or smugglers (allegedly) stashed their rum caches. Bring sunscreen, a waterproof bag for your camera, and a healthy sense of humor about damp shorts. Ultimately, even if caves aren't normally your thing, a visit to Benagil is like finding yourself at Portugal's geological Coachella-touristy, yes, but unforgettable enough to brag shamelessly about later over multiple glasses of vinho verde.