According to google searches, the Jinping Underground Laboratories are the "deepest" building or buildings constructed, reaching 7900 feet (2400 metre) below the surface.... However, the surface in question is a mountain. While that does classify as underground, it highlights a flaw in the question of the deepest underground building.

I can't seem to find the lowest building in the world though, or the deepest in relation to depth within the earth's crust.

What is the lowest point below sea level that we have built where a human can go? I imagine this is likely another laboratory. But where would a building of this description be?

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    $\begingroup$ Does it have to be a fixed structure? Diving submarines have gone rather dramatically below sea level. $\endgroup$ Commented Jan 11, 2022 at 15:08
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    $\begingroup$ @CarlWitthoft We're looking for a fixed structure, yes! I know there's some pretty deep expeditions undersea. $\endgroup$ Commented Jan 11, 2022 at 17:04
  • $\begingroup$ The thickness of the Earths crust varies significantly, so you could be in the Earths crust at the same depth you would be far in the mantle in other places. The crust varies roughly in the range of 5 to 30 km. $\endgroup$ Commented Jan 13, 2022 at 4:34
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    $\begingroup$ "depth within the earth's crust" Depends how you want to measure. Because the Earth is wider than tall, standing at the poles you're 22km closer to the centre of the Earth than you are at the equator - both at sea level. Are you asking strictly about the closest you can get to the centre of the Earth? $\endgroup$
    – J...
    Commented Jan 14, 2022 at 2:02
  • $\begingroup$ Related to, What practical geographical and engineering constraints limit the depth to which you can build underground?. $\endgroup$
    – Fred
    Commented Jan 14, 2022 at 3:10

4 Answers 4


The Kidd Mine in Ontario, Canada: per the Wikipedia article, it is "the deepest accessible non-marine point on Earth" at "2,733 metres (8,967 ft) below sea level". I found this from the Wikipedia article on Extremes on Earth, which differentiates between depth from the surface and depth below sea level, and also between an actual mine vs. a bore hole.

  • $\begingroup$ The source for that wikipedia fact is based on a claim made in an article in the Canadian Mining Journal (a magazine/news company, not an academic journal) in 2007. The articles make it more clear that there are deeper mines (ie:Mponeng, etc) when measured from the surface, but that the Kidd mine represents the closest non-marine accessible point to the centre of the Earth - a claim they don't provide any reference for either. It is currently the deepest base metal mine, at least. $\endgroup$
    – J...
    Commented Jan 14, 2022 at 1:55
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    $\begingroup$ @J... The OP specifically asked for deepest below sea level, not deepest from the surface. The elevation of Carletonville, South Africa, where Mponeng is located, is >1.5km above sea level, so the depth below sea level of Mponeng is probably around 2.5km or less, less than the Kidd Mine. I think the Kidd Mine is a reasonable contender for deepest below sea level given the below sea level measurement given, but if you find another that would be interesting. $\endgroup$ Commented Jan 14, 2022 at 18:24
  • $\begingroup$ (As pointed out in another comment, of course, closets to the Earth's center is a very different beast. Even if you only consider artificial structures, there are probably some buildings further north which are technically closer to the Earth's core while being above ground. But I think the OP is pretty clear about being interested in depth and specifically relative to sea level.) $\endgroup$ Commented Jan 14, 2022 at 18:34
  • $\begingroup$ Agreed, and Mponeng is also only 26.4S in latitude, while the Kidd mine is 48.6N, so it is also significantly closer to the poles with sea level there being closer to the centre of the earth as well. $\endgroup$
    – J...
    Commented Jan 14, 2022 at 21:03

I assume you are asking the deepest structure of any sort that exists. Here is an infographic :

The Deepest Underground Structures in the World – AlansFactoryOutlet.com – Infographic Source : https://alansfactoryoutlet.com/the-deepest-underground-structures-in-the-world/

One mystery undersea structure:

Cuban Underwater City

The Cuban Underwater City is another underwater structure that raises more questions than it answers. What appears to be ruins of a submerged city with corridors and buildings including massive granite complexes, pyramids and circular structures is located off the coast of western Cuba as much as 2,000 feet (650 meters) below the sea level. According to the scientists, it would take about 50,000 years for the alleged city to be submerged to its current depth. As a result, many expressed doubt that the researchers from a Canadian company really discovered a lost ancient city in 2001. Unfortunately, sonar and underwater video robot images are everything that the researchers have so far about the site. Until more is known, it is impossible to say what is down there although the possibility that it is really a lost ancient city cannot be ruled out either.


Note: THe deepest descent in the ocean by human

"1960: Jacques Piccard and Don Walsh, with the deep sea vessel Trieste, descend to the bottom of the Challenger Deep in the Mariana Trench (10,740 meters/6.67 miles). They observe fish and other organisms. Fish were not thought to inhabit such deep water."


  • $\begingroup$ That did help me actually, because the indicator of being beneath a mountain! Although, it's not exactly what I'm looking for. It's close enough. I was looking for the closest building (such as a lab or basement) to the core of the earth. I knew the borehole was the deepest artificial point, and that the mines were deep. $\endgroup$ Commented Jan 10, 2022 at 21:36
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    $\begingroup$ The pictures in your answer only show depth below ground, not below sea level (what OP is asking). The Gotthard Base Tunnel is certainly not 2km below sea level. $\endgroup$
    – Michael
    Commented Jan 11, 2022 at 8:12
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    $\begingroup$ yep, even those without a mountain marker next to them are still accounted from the ground level, not sea level $\endgroup$
    – Hobbamok
    Commented Jan 11, 2022 at 11:26
  • $\begingroup$ True, while not exactly the specific I was looking for, it does give me a much better answer than the 30 results saying under-mountain complexes are the deepest when you can drive horizontally into them. r13 definitely has helped me in this search! I appreciate your help! SolarMike You're correct, I should have been more clear in what I did find. $\endgroup$ Commented Jan 11, 2022 at 13:39
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    $\begingroup$ @ChrisGergler note that "closest to the core of the earth" is not exactly the same as "deepest under sea level", as the earth (at sea level) is not a perfect sphere, but flattened on the poles due to the rotation. That's a difference of 42 km, much more than the deepest structure is away from the surface. So I guess you'll get a somewhat deep tunnel near the poles. $\endgroup$ Commented Jan 12, 2022 at 0:57

If your volunteer is a very small person, maximum shoulder width of 23 cm/9 inches, then the answer is 12,262 metres (40,230 feet) deep in the Kola superdeep borehole in Russia.
I can't find the "height above sealevel of the start" to subtract from total depth of borehole, sorry. Best I can find is 230 metres above sea level.

They probably won't come out alive due to heat and lack of oxygen, but that was never stated as a requirement.

Temperatures were measured as 180 °C (356 °F) and the rock became too "plastic" to drill.

In free-air it would take around 220 seconds to fall this far based on 55 m/s terminal velocity of a human, but given the hole has a limited size, and the descending person has a width, there will be resistance to the air moving past. Plus any rising heat will act as a thermal, potentially lifting the descender. Additionally, friction with the side walls and any blockages will slow one's descent.


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    $\begingroup$ I'm dying at the statement, "They probably won't come out alive..." Thank you for your answer, but Kola Superdeep Borehole wasn't what I was looking for. $\endgroup$ Commented Jan 11, 2022 at 13:35
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    $\begingroup$ "maximum shoulder width of 23 cm/9 inches" If we are going full hog, accommodations/modifications could be made to assist in this problem... $\endgroup$
    – Aron
    Commented Jan 12, 2022 at 7:27
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    $\begingroup$ @Aron That might be taken care of by the 55 m/s (200 kph, 120 mph) friction with the side walls. $\endgroup$
    – dotancohen
    Commented Jan 13, 2022 at 12:29
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    $\begingroup$ That's one hell of an Ättestupa! $\endgroup$ Commented Jan 13, 2022 at 13:04

The point you are looking for is very likely located in a mine. You could check the list of deepest mines by depth below ground, and then find and subtract the surface elevation for each. (This still assumes humans can go to the deepest points of these mines, which may or may not be correct.)


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