At 1.8 billion years old, this UNESCO World Heritage Site in the Brazilian Highlands is the oldest rock formation on earth. The washed out grey rocks in the Vale da Lua, or Valley of the Moon, have been smoothed and shaped by the clear waters of the San Miguel River, which runs across it. Over the years, the water has drawn sand particles across the rock surface, creating friction and digging craters.
When to go: Since heavy downpours during the rainy season mean that the river is always flowing and temperatures are always tolerable, you can visit at any time. Bear in mind that high season in Brazil runs from the end of December through March, so prices for flights and accommodations will be pricier then. You do not need to worry too much about crowds at Valley of the Moon, though: many locals aren't even aware of its existence.
What to do: The Valley of the Moon is situated within Chapada dos Veadeiros National Park, which covers 253 square miles of land. Only three percent of the park is open to tourism; the remainder is used for research or preservation. You can see endangered species like pampas deer, maned wolves, and giant armadillos within the park, as well as 25 variations of orchids unique to the area. You can also hike up the 1,315-foot-high Serra de Santana peak, the highest point within the park, and explore the many waterfalls and canyons.