Lava Tubes on the Moon and Mars are Really, Really Big. Big Enough to Fit an Entire Planetary...

And those tubes are attracting more and more attention, as future plans for a habitat of some sort on both worlds are taking shape.

Sgt (Join to see) Maj William W. 'Bill' Price Lt Col John (Jack) Christensen

reminds me of the Arnold Schwarzenegger movie Total recall

Very interesting and informative. Thank you for the share.