Waitomo Glowworm Caves, Waitomo, North Island, New Zealand

Geology
Geological and volcanic activity has created around 300 known limestone caves in the Waitomo region over the last 30 million years.
The limestone formations in the Waitomo Glowworm Caves were formed when the region was still under the ocean about 30 million years ago. The limestone is composed of fossilized corals, sea shells, fish skeletons, and many small marine organisms on the sea beds. Over millions of years, these fossilized rocks have been layered upon each other and compressed to create limestone and within the Waitomo region the limestone can be over 200 m thick.