Vanuatu Post’s Underwater Post Office, just off Hideaway Island near Port Vila, Visitors from around the world have literally donned their mask and snorkels, postcards in hand to experience the world’s first underwater post office. The Post Office is only 50 metres offshore and at just three metres below the surface, is very accessible I'm happy to say I have posted a letter there too!
Ion Luxury Adventure Hotel in Sellfoss ca. 45 min from Reykjavik on gravel road part of way. Depending on time of year - in winter you might need 4 wheel drive, and make sure which road to take as one of the mountain roads close during winter