The numbers give rise to the reason: There were 25 million international tourists in 1950. Last year, more than one billion globetrotters set out to see the world’s cultural and natural wonders—from the Serengeti’s Great Migration to the ancient Inca cities of Peru. We now have more places to go and more ways to get there than ever before. With that comes an even greater responsibility to safeguard our fragile planet for future generations.As the United Nations heralds 2017 as the International Year of Sustainable Tourism for Development, one place rises above the rest: Slovenia. Last year this Adriatic enclave, nestled amid emerald fields, snowy peaks, and sparkling waters, was declared the world’s most sustainable country. Slovenia achieved an eye-opening 96 out of 100 detailed sustainability indicators (think environment and climate, culture and authenticity, nature and biodiversity, among others.) And its quaint capital Ljubljana was also anointed Europe’s Greenest Capital in 2016 by the European Union.