Wieliczka salt mine
Coober Pedy is a town in northern South Australia with a population of 3,500 and over 45 different nationalities. Coober Pedy is famous for below ground residences, called “dugouts”, due to the burning daytime heat.
The aerial view shows a city with no buildings.
One of the underground churches in Coober Pedy
Salt mines are all kinds of fun in lots of different ways. Here are a couple memorable ones from Salzburg:
http://2.bp.blogspot.com/-4WSYSsvOgvk/TkBFHNuWFwI/AAAAAAAAAj4/Jzek01NudfA/s1600/SAM_0020.JPG
The second one is the recreation if the actual corpse they found in the mines, mummified by the salt.
I borrowed these from this blog post, since I don’t have with me the ones I took when I visited.
Of course, all I can think of now is giant fucking spiders. Thanks, years of gaming + military service. No sleep tonight. 
This place is like a real-life Mega-City-One. Imagine a fantasy version, of course.
http://www.dailymail.co.uk/news/article-2139914/A-rare-insight-Kowloon-Walled-City.html
“World’s largest cave” in Vietnam:
Article: http://www.huffingtonpost.com/2013/09/07/son-doong_n_3873341.html?ncid=edlinkusaolp00000009
[video=youtube_share;SKAXw4mzgIo]http://youtu.be/SKAXw4mzgIo[/video]
Pinara in Southern Turkey:
[video=youtube_share;e3k1gFcmujg]http://youtu.be/e3k1gFcmujg[/video]
This guy posts quite a lot of interesting videos, both RPG and non-RPG related. For example, he has quite a few videos posted about weapons, armour and military tactics.
The tombs of Pinara (cut into cliff face):
[video=youtube_share;C9d2xw_sH94]http://youtu.be/C9d2xw_sH94[/video]
Too bad they don’t qualify “largest”…
The only hard data I find is that it’s got the largest passage at 5000m x 145m x 200m.
Not sure how that compares to the worlds longest (known) cave which is Mammoth Cave in Kentucky at 643.7km in length of mapped passages.
It would be interesting to see how estimated volume of the caves would compare…
This site lists the worlds longest caves:
http://www.caverbob.com/wlong.htm
This site lists the worlds largest cave chambers and passages (and includes Han Son Doong):
http://www.caverbob.com/room.htm
Ignoring all of this nit picking, the cave is impressive.
Frank
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//youtu.be/FHeel1GNFFY
Ajanta Caves
2000 year old temples carved into a mountainside in India.
About five minutes in the commentary goes all whacko on alien theories, but nonetheless a cool site.
Can imagine secret doors in each of those caves aligned with the rising sun on the solstices, that only open when the sun shines directly on them.
That’s hilarious. I like the assumption that early humans were completely incapable of imagination or creativity (one of the fundamental components of human intelligence). Sorry, off topic. 
This is also very attractive for some Torchbearer inspiration:
http://www.huffingtonpost.com/2013/09/07/son-doong_n_3873341.html
The article takes some liberties with the real nature of this lake. In actual fact flamingos breed there and there are some fish in certain parts of it that aren’t so alkali, but the photos are great and in a fantasy world it certainly could petrify everything…
Yeah, I saw this article posted on Digg or something yesterday, and was expecting to actually see it show up here. However, I was assuming it might end up in the Mouse Guard zombie ants thread rather than this one.