This Australian lake is the color of bubble gum! Scientists are not sure why. They say the pink color could come from certain microorganisms, or tiny living things.
Jim McMahon/Mapman® (map); Aussie oc/CC/Wikipedia (Lake Hillier)
2. Easter Island
This island in the Pacific Ocean is famous for its giant stone statues. There are more than 800 figures, called moai (MOH-eye). They were carved long ago by the island's native people— but no one knows why.
Chakarin Wattanamongkol/Getty Images (statues); Jim McMahon/Mapman® (map)
3. Eye of the Sahara
Look at Africa's Sahara desert from outer space, and you might see this giant bull's-eye. It's a rock formation that is about 25 miles wide. How it formed is a big mystery.
World History Archive/Alamy Stock Photo (eye); Jim McMahon/Mapman® (map)
4. Cliff Cities
About 800 years ago, Native Americans built hundreds of homes along the cliffs of Mesa Verde in Colorado. Then they suddenly abandoned the cities. What could have caused them to leave?
Jim McMahon/Mapman® (map); Harald Lange/Ullstein Bild via Getty Images