Reventón del Rio Mundo, Natural waterfall in Sierra del Segura, Spain.

Reventón del Rio Mundo is a waterfall in the Sierra del Segura that emerges from a cave opening and descends in a series of cascades. The water collects in natural pools as it flows down the mountainside before continuing into the valley below.

The waterfall pours from a cave 15 metres wide and 25 metres high at the end of a large cave system beneath the Calar del Mundo plateau. The Mundo then flows 150 km west to join the Segura south of Hellín. The Camarillas reservoir on its lower course caused small earthquakes when first filled in spring 1961; the tremors stopped in spring 1962.

The sudden surge is called el reventón or los Chorros del río Mundo, and locals watch for it after heavy rain or the spring thaw of snow on the Calar del Mundo. The source lies just outside Riópar, and the whole site sits within the Parque Natural de los Calares del Río Mundo y de la Sima, one of five natural parks in Castilla-La Mancha.

Access is best done on foot along a marked trail that runs through the riverbed and past the cave opening. Sturdy shoes are essential, and care is needed on wet rocks since the path can become slippery.

The water does not emerge from the surface but flows out through a cave opening where it comes from underground rivers running through the entire mountain mass. This hidden origin makes it a rare example of how underground water systems can carve through stone over time.