Curonian Spit National Park, Lithuania.

There’s nowhere in the world that’s quite like the Curonian Spit—in fact, the place is unique enough that it’s been designated a UNESCO World Heritage Site. So what exactly is it, you may be asking? It’s a long, narrow strip of sprawling white sand dunes and 100-year-old pine groves that stretches along the edge of the Baltic Sea, forming the edge of the Curonian Lagoon. There are plenty of prime spots for sunbathing along the dunes; for the more active traveler, you may choose to hike or cycle through the area—just make sure to stay on the marked paths since the shifting sands and fragile ecosystem mean that straying from the beaten paths can do serious damage to the park!