I have and use Goggle Earth (Pess showed it to me) but there are limits to what it shows. Also much of the property listed does not provide correct address or coordinates. Many of the GE scans are very old and the conditions have changed. I use GE to narrow the search but sometimes you just have to look that gift horse in the mouth. The property around Douglas AZ, looked promising (price wise) but was down in the valley and way to flat. I might as well have installed a Light house beacon showing the way. OR a big neon flashing sigh "Come and Get Me". I have plenty of time and no fixed location except --- no snow, ever! Of course that also means no close or visible neighbors. The hidden cul-de-sac is ideal and I will keep hunting. I am hoping to find land that is worthless for traditional farming or ranching and not near any I do miss Pess and out off line conversations /debates. It is so easy to overlook the obvious and have additional / opposing view points can and does eliminate the mistakes. I decided to look for the land and figured better to buy it now and build late, maybe even a generation later but at least secure a safe viable family site. I think it will be Texas, Arizona, New Mexico or maybe Nevada. I have my doubts about Nevada due to their liberal leaning politics. i drive a site in Nevada that looked extremely viable but did not stop to check it out or even look around. maybe I can find it again on GE. I should have noted which town we were driving by. Oh, well happy hunting time.
Now as for the cavern. The only thing I could figure out was to conceal the entrances, Store food, water, ammo, drones, medical supplies and some spare communication gear. Then the cavern would be a secure fall back position. I think the winters would be a reasonable safe time (snow on ground leaves tracks) but any other season you might need to make a hasty and hopefully temporary departure. This safe stockpile would allow you and the other folks at the Retreat to formulate a plan to reclaim your compound from any uninvited guests. The Retreat already has most of the modern comforts, the only thing lacking an advanced intrude alert system and a renewable food supply. A Pearl Harbor type event could force your group to vacate but you would HAVE to reclaim your supplies and shelter. The same applies for the THH project and measures are planned to perform this task too. Alarms are required but they will not mitigate over whelming numbers. 50 against 5 is not going to work out to well for the 5 if they stay and try to hold their ground. An escape rout is required but neither of us can afford to loose the supplies or the shelter. Pess and I did discuss methods to discourage intruders but we did not discuss the method to reclaim the compounds. That is something you, Robocop, and Pess (?) should discuss.