Look at the size of this pumpkin on the banks of the Colorado River! It's not a garden pumpkin, though, it's made of mineral deposits. This is Pumpkin Spring, named for the obvious reason. The pumpkin is the result of a warm mineral spring that deposited limestone as it met the river, creating a natural pool. The water churns inside and then spills over the top, leaving orange streaks down the outside, giving it an autumn harvest color.
Inside, Pumpkin Spring is more like a witch's cauldron than a gourd. The warm water contains all kinds of dissolved metals, including a high concentration of arsenic. Yes, people swim in it, although it is not recommended, and it is forbidden to drink the water. It is the most poisonous water in the Grand Canyon. Pumpkin Spring is not that easy to get to, anyway. There are no trails, but if you're boating down the river, you'll find it at mile 212.9. See more of Pumpkin Spring at Atlas Obscura, where it is today's "place of the day."
(Image credit: Nate Loper)