DENMARK, GERMANY, THE NETHERLANDS // Unesco-anointed for being the world's largest expanse of intertidal sand and mud flats, Wadden Sea National Park sprawls across three countries' territories, and is a habitat for diverse plants and animals. There's much to learn at the park's visitor centres, but take a boat trip to one of the islands, such as Texel in the Netherlands or Denmark's Fan to experience idyllic coastal settlements. In autumn, witness up to a million starlings taking to the skies to perform a sky-obliterating murmuration.