Parque Nacional dos Lençóis Maranhenses - "The Bedsheets of Maranhao"
Probably the coolest, most surreal landscape I've ever been lucky enough to visit. This is located in the northeast of Brazil, far from the well-trodden path of Sau Paulo and Rio de Janeiro. There is impenetrable rock underneath the sand, which prevents rainwater from draining through. The result is these green/blue lagoons throughout the sand dunes, as far as the eye can see. Cannot recommend it highly enough!