Looking for one of the most luxurious and unique spa experiences in the world to ring in another year around the sun? Look no further than Bermuda for your next birthday bash, where you’ll have the chance to enjoy a massage inside a 500,000-year-old grotto courtesy of Grotto Bay Beach Resort & Spa’s Natura Spa. A little background, the property innovatively helped its guests tick off their wanderlust, wellness and mermaid goals when it created this subterranean spa, located inside a grotto filled with spectacular stalagmites and stalactites. Fun fact: It's named after the famed Shakespearean character from “The Tempest,” Prospero.