Lake Castrovalva offers unique and other worldly formations. Pictured here, giant cave mammillaries that were once underwater and part of the main lake. These formations are known as 'lions tails' because the mammillary on the end of the stalactite looks like a lions tail. Everything we wore and took into Lake Castrovalva had to be super clean. We had to change our clothes before entering this pristine section of Lechuguilla.