Nestled in a cave that overlooks the Adriatic Sea in the South of Italy lies one of the world's most romantic restaurants: the Grotta Palazzese. It's exactly where you'd expect to find one too.

Some of the most amazing spectacles around the world are hidden deep underground, beneath rocks, sea and even ice.

Visitors can take a rowboat or a private tour to discover this cave where the water turns a glittering emerald hue in the ...