Costa Rica, already officially the happiest country in the world, must be grinning away because sustainable just got sexy.  The United Nations has declared 2017 the International Year of Sustainable Tourism for Development, and this global leader in sustainability has just found itself the perfect opportunity to flaunt its most enviably gorgeous eco-resorts. Costa Rica is ahead of the world, producing nearly 93 percent of its electricity from renewable resources and conserving almost 30 percent of its national territory.  The country is also on track to become the first carbon neutral nation in just a few years.  At the forefront of Costa Rica's sustainable tourism is the Cayuga Collection, comprising by far the sexiest ecolodges, resorts, and hotels throughout Costa Rica and Nicaragua.