More ideas from Vendy
Fingels Cave in Scotland (apparently was misrepresented by name and location when I repinned it from another user.)

Hengill, Iceland - Hengill was formed from a Palagomite tuff, it is a central volcano and has a giant magma chamber beneath it. When thick basalt lava flows cool, they form hexagonal cracks, called columnar joints

Hydrospeed dans un glacier! Je DOIS le faire! Enfin on rediscute quand même de la température de l'eau;) http://www.version-oxygene.com

There are two major dangers when sliding head first through glacial runoff. But despite the risks, the of hydrospeeding has emerged as a glacial summertime hobby.