Undarra lava tubes

A closed national park (for our safety they assured us) but truly world class - 60km of tubes (all tubes combined) and the next nearest is Hawaii with only 20km.

Apparently the lava on top of the flow hardened, and allowed the hotter molten lava inside the tube to continue flowing......hence the tube. In the ensuing 190,000 years, erosion has caused some to collapse but many remain, to surprise the unaware, in the middle of dry savannah vegetation. Micro bats live inside and fluttered around when our guide shone a torch on them.