The Mocona Falls almost seems to defy logic.
The 2.4 kilometre-long waterfall forms when water levels lower along a split-level channel on the Uruguay River in Argentina, close to the border with Brazil.
The effect is of a river falling sideways — and it looks like a feature on an alien planet.
The waterfall, which is only visible for about 250 days per year, is almost 12 metres high in places.
When the water levels are a bit higher, the river becomes rapids at this point.
Mocona means "that which swallows everything" — and these pictures show just why it was given such a dramatic name.