Charco Azul is one of El Hierro's most photogenic natural swimming pools, a pocket of clear Atlantic water held inside black lava rock on the island's north coast. Steps and platforms make access easier than at wilder coves, but the place still feels shaped by volcanic stone and surf.
Go in calm weather and check conditions before swimming, because waves can still surge into the pool. Outside the water, the contrast between dark cliffs, blue sea, and the El Golfo coast makes it a worthwhile stop even for non-swimmers.