2Cave of the Crystals, Mexico
Few caves on Earth look as otherworldly as the Cave of the Crystals in Naica, Mexico. It contains enormous gypsum crystals, some of which reach several meters in length.
The crystals formed under highly unusual geological conditions involving mineral-rich groundwater and heat beneath the Earth’s surface. Their extraordinary size makes the cave one of the most fascinating geological environments ever documented.
However, the extreme temperatures and humidity inside the cave make it unsuitable for ordinary tourism. It is therefore best regarded as a remarkable geological wonder rather than a conventional visitor attraction.
