# What is the largest underground space that we could build? **URL:** \ **Category:** Factual Questions\ **Created:** [July 18, 2009, 5:35pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457 "2009-07-18T17:35:33Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [October 11, 2014, 12:52am UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/21 "2014-10-11T00:52:55Z")
> [@Sunspace](#): > > Another crazy idea that came to me in the shower… > > I got to thinking about underground lairs and whatnot à la Blofeldt. How big an underground space could we build? There seem to be at least three possibilities:[ol][li]Roofing over an existing hole.[/li]I’m imagining a dome over an open-pit mine. How big a dome could we built, and still cover it with dirt to make the ground level? If this is doable, I have some ideas involving the [Vortex of Doom](http://www.usmra.com/photos/bigpit/003.jpg).[/ol] The [Akashi Kaikyō Bridge](http://en.wikipedia.org/wiki/Akashi_Kaiky%C5%8D_Bridge) is alleged to have a main span of 1991 meters. If you don’t mind pillars and cables sticking out of the ground, you could build a great many of them, side-by-side and cover the roadway with dirt. This would get you an area 1991 meters wide and indefinitely long. One cost around 500 billion yen, but you could probably get a volume discount. 🙂 ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [October 11, 2014, 12:56am UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/22 "2014-10-11T00:56:32Z")
Oh, and **Bazlord** , welcome to the board. We always appreciate well written informative posts, even five years late. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [October 11, 2014, 2:03pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/23 "2014-10-11T14:03:57Z")
Does he know that zombies often live in underground spaces? ---
**Author:** ![rbroome](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@rbroome](https://boards.straightdope.com/u/rbroome)\ **Post date:** [October 12, 2014, 2:29pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/24 "2014-10-12T14:29:17Z")
> [@Cartooniverse](#): > > A few moments of Googling will reveal that all of the space you see as you meander around Walt Disney World in Florida has at least one level BELOW it. ALL of the space. There is an entire complex under the ground. It may only be one floor deep. But it’s titanic. Disneyworld follows the OP, but remember that due to the high water table in the area, the center of Disneyworld is 2 stories high. The tunnels aren’t actually underground, the center 9 acres was built above ground then covered with fill. ---
**Author:** ![Claverhouse](https://avatars.discourse-cdn.com/v4/letter/c/13edae/32.png) [@Claverhouse](https://boards.straightdope.com/u/Claverhouse)\ **Post date:** [October 12, 2014, 3:28pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/25 "2014-10-12T15:28:56Z")
The **[Wieliczka salt mine](https://en.wikipedia.org/wiki/Wieliczka_Salt_Mine)** in Kraków province, which I read of recently in the Strand Magazine, when it was the Hapsburg Royal Salt Mine, has an underground lake with boating facilities, a cathedral and three chapels all made of salt; is 1,073 feet deep and 178 miles long. Admittedly it is not one single chamber, but it must include some fairly big spaces. It ran from the 13th century to 2007. ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [October 12, 2014, 4:10pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/26 "2014-10-12T16:10:38Z")
What about underground natural gas reserves – is that all open space filled with gas? The Haynesville shale, under coastal Louisiana, contains 250-trillion cubic feet of gas, which by my calculation is roughly 1,600 cubic miles, some 2-3 miles below the surface. The would be equal to a room with a 1,000 foot ceiling, the size of New Jersey. Even if it is not conveniently shaped like a room, it would eliminate the troublesome necessity to remove solid material to the surface, it could all just be rearranged underground. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [October 12, 2014, 4:52pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/27 "2014-10-12T16:52:12Z")
> [@jtur88](#): > > What about underground natural gas reserves – is that all open space filled with gas? The Haynesville shale, under coastal Louisiana, contains 250-trillion cubic feet of gas, which by my calculation is roughly 1,600 cubic miles, some 2-3 miles below the surface. The would be equal to a room with a 1,000 foot ceiling, the size of New Jersey. > > Even if it is not conveniently shaped like a room, it would eliminate the troublesome necessity to remove solid material to the surface, it could all just be rearranged underground. I believe it is porous rock, not actual cavities. ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [October 12, 2014, 6:02pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/28 "2014-10-12T18:02:45Z")
> [@Lumpy](#): > > I believe it is porous rock, not actual cavities. I presume, then, that porous rock can be pulverized and compressed, to leave large cavities with more compacted rock left behind? Kind of like putting a hot poker through styrofoam, to compact porous material. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [October 12, 2014, 9:10pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/29 "2014-10-12T21:10:31Z")
Did anyone mention [Subtropolis](http://en.wikipedia.org/wiki/SubTropolis) yet? 55 million square feet of man-made space with about seven miles of internal roads used for cool, dry storage. And [data](http://www.subtechkc.com). ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [October 12, 2014, 9:45pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/30 "2014-10-12T21:45:02Z")
> [@chorpler](#): > > Could we build something like that big chamber in the Mines of Moria scene in the first **Lord of the Rings** movie? Closest that I have seen: The Tokyo Flood Tunnels: > **[G-Cans Project, Tokyo – Japan’s $2.6 Billion Flood Tunnel – FloodList](https://floodlist.com/protection/g-cans-project-tokyo-flood-tunnel)** (scroll down for the view of the huge chambers with Moria like columns.) Not sure how effective for a zombie apocalypse. (I noticed now that this is a zombie thread) ---
**Author:** ![the\_diego](https://avatars.discourse-cdn.com/v4/letter/t/7bcc69/32.png) [@the\_diego](https://boards.straightdope.com/u/the_diego)\ **Post date:** [October 13, 2014, 4:44am UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/31 "2014-10-13T04:44:15Z")
This was in the 70s but the biggest underground excavation meant for storage are those crude oil storage tanks. As additional doper knowledge, the longest echo was generated in one of them. [Now we've heard it all: Acoustic scientists shatter the world record for longest ever echo | The Independent | The Independent](http://www.independent.co.uk/news/science/now-weve-heard-it-all-acoustic-scientists-shatter-the-world-record-for-longest-ever-echo-9062134.html) Engineering-wise, a cavernous storage space is different from several ramifying “human-sized” tunnels, even those with multiple levels. The latter is much easier to excavate and maintain. Mines do it all the time. Regarding natural caves, I at least know that limestone cave networks are not enduring, even within the span of a lifetime. Limestone caves collapse regularly. ---
**Author:** ![The\_Joker\_and\_the\_Thief](https://avatars.discourse-cdn.com/v4/letter/t/e79b87/32.png) [@The\_Joker\_and\_the\_Thief](https://boards.straightdope.com/u/The_Joker_and_the_Thief)\ **Post date:** [October 13, 2014, 5:48am UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/32 "2014-10-13T05:48:50Z")
On a different note, the [largest](http://www.istructe.org/journal/volumes/volume-79-%28published-in-2001%29/issues/issue-21/articles/the-world-s-largest-self-supporting-enclosed-space) above ground structure is the Tropical Island Resort, a fake tropical paradise built inside a giant former aircraft hanger in Germany. It has a volume of [5.5 million](http://www.amusingplanet.com/2012/11/tropical-island-resortworld-largest.html) cubic meters, and presumably that could be increased substantially if the ground below it was excavated. The size of the oil storage container mentioned below is at most 18000 cubic meters, so it’s not even on the same level–though I imagine you could just extend the length indefinitely. ---
**Author:** ![MostlyUseless](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@MostlyUseless](https://boards.straightdope.com/u/MostlyUseless)\ **Post date:** [October 13, 2014, 11:34am UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/33 "2014-10-13T11:34:30Z")
You might want to check out the Dotiki coal mine in Madison County, Kentucky. The mine underlies the entire county three levels deep and they may, by this time, be working on the fourth layer. Longwall miners using room and pillar techniques + lots of time = vast underground areas. ---
**Author:** ![Snarky\_Kong](https://avatars.discourse-cdn.com/v4/letter/s/a183cd/32.png) [@Snarky\_Kong](https://boards.straightdope.com/u/Snarky_Kong)\ **Post date:** [October 13, 2014, 12:04pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/34 "2014-10-13T12:04:06Z")
> [@jtur88](#): > > What about underground natural gas reserves – is that all open space filled with gas? The Haynesville shale, under coastal Louisiana, contains 250-trillion cubic feet of gas, which by my calculation is roughly 1,600 cubic miles, some 2-3 miles below the surface. The would be equal to a room with a 1,000 foot ceiling, the size of New Jersey. > > Even if it is not conveniently shaped like a room, it would eliminate the troublesome necessity to remove solid material to the surface, it could all just be rearranged underground. Not only is the gas in porous rock, but it’s under pressure, and would occupy far less volume than at STP. For a spherical cavity in an infinite homogenous medium, the tangential stresses at the cavity boundary are twice the geostatic stresses ([http://www.usucger.org/PandD/Chapter%2011.pdf](http://www.usucger.org/PandD/Chapter%2011.pdf)) . Taking the compressive strength of rock as 30 ksi and the density as 150 pcf, you could have a sphere with a diameter of 14,400 ft that is only supported by the rock mass. Now, that elastic solution isn’t valid due to the ground surface being close, there’s no factor of safety, and I’m assuming there are no defects or stress concentrations anywhere. Should give some sort of order of magnitude idea though. ---
**Author:** ![clairobscur](https://avatars.discourse-cdn.com/v4/letter/c/839c29/32.png) [@clairobscur](https://boards.straightdope.com/u/clairobscur)\ **Post date:** [October 14, 2014, 8:09am UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/35 "2014-10-14T08:09:28Z")
> [@Johanna](#): > > Not as an example of great size, but as a bodacious work of art: [The Temples of Damanhur](http://www.thetemples.org/). Those Italians! That’s something. I started the virtual tour only to notice that n the second or third “temple” they depict naked men while hiding or even simply not including the genitals. I’m amazed to find prudishness in such a place. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [October 14, 2014, 12:54pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/36 "2014-10-14T12:54:07Z")
> [@the\_diego](#): > > Regarding natural caves, I at least know that limestone cave networks are not enduring, even within the span of a lifetime. Limestone caves collapse regularly. Thats not true. Caves almost by definition form over geologic time. The erosional processes that create the voids occur over LONG periods of time. Any big cave that isn’t a buried pile of rubble has been around a long damn time by human standards. And the buried one even longer, its just not big anymore. ---
**Author:** ![Kimballkid](https://avatars.discourse-cdn.com/v4/letter/k/b5a626/32.png) [@Kimballkid](https://boards.straightdope.com/u/Kimballkid)\ **Post date:** [October 14, 2014, 9:29pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/37 "2014-10-14T21:29:15Z")
The former Homestake Gold Mine/current Sanford Underground Research Facility in the Black Hills of South Dakota is 8,000 feet deep. I couldn’t find anything about how wide/long it is though. ---
**Author:** ![Mr.Milton](https://avatars.discourse-cdn.com/v4/letter/m/6bbea6/32.png) [@Mr.Milton](https://boards.straightdope.com/u/Mr.Milton)\ **Post date:** [October 15, 2014, 1:12pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/38 "2014-10-15T13:12:43Z")
[http://www.theguardian.com/travel/gallery/2014/jan/14/take-a-look-inside-the-worlds-largest-cave](http://www.theguardian.com/travel/gallery/2014/jan/14/take-a-look-inside-the-worlds-largest-cave) Son Doong cave in Vietnam, recently featured in National Geographic, is said to be the world’s largest. At least 5x larger than Malaysia’s Deer Cave. [http://mysteriousuniverse.org/2014/09/the-lost-forest-world-of-the-worlds-largest-cave/](http://mysteriousuniverse.org/2014/09/the-lost-forest-world-of-the-worlds-largest-cave/) ---
**Author:** ![the\_diego](https://avatars.discourse-cdn.com/v4/letter/t/7bcc69/32.png) [@the\_diego](https://boards.straightdope.com/u/the_diego)\ **Post date:** [April 25, 2015, 11:51pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/39 "2015-04-25T23:51:56Z")
> [@billfish678](#): > > Thats not true. Caves almost by definition form over geologic time. The erosional processes that create the voids occur over LONG periods of time. Any big cave that isn’t a buried pile of rubble has been around a long damn time by human standards. And the buried one even longer, its just not big anymore. how many times have you heard on the news that a giant, ungodly deep hole appeared at a street or one’s backyard? A sinkhole is the roof of a cave that has collapsed. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [April 26, 2015, 2:29pm UTC](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457/40 "2015-04-26T14:29:41Z")
And how many voids that have yet to collapse do you think there are? [Previous page](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457.md?page=1) [Next page](https://boards.straightdope.com/t/what-is-the-largest-underground-space-that-we-could-build/503457.md?page=3)