You are Alien McGee. For some reason ( don't ask why ) you need to hide an artifact in our solar system for roughly 20,000 years before coming back and taking it.

Said artifact is a magical vase that requires 1 GJ a day. If it doesn't obtain said energy, it will turn to dust. Any excess will simply disappear into NowhereLand, unless the total exceeds 10 GJ, then the vase once again turns to dust.

When you return, the vase must be intact, but most importantly, you should be capable of easily retrieving it ( and finding it in the first place ).

How would you build this dungeon?

  • The dungeon must last at least 20,000 years.
  • You have a maximum volume of 5km^3 at your disposal ( any shape you want )
  • It must be hidden. This means nothing is allowed to leave the dungeon, and that the dungeon itself must not passively or actively make it's location known. As such, that means no nanobots, no self-aware AI or anything that could accidentally wander outside the dungeon.
  • It must also be self-sufficient. By that, I mean it must not be required to obtain any materials from outside the dungeon.
  • The dungeon must generate 1 GJ a day, everyday, non-stop, for 20,000 years.
  • Any technology that doesn't break the rules is at your disposal, as well as any resources
  • The dungeon can be built on any celestial body in the solar system, but can't be in orbit or on be on the surface.
  • $\begingroup$ just make a giant battery $\endgroup$
    – Topcode
    Commented Apr 4, 2020 at 18:12
  • 3
    $\begingroup$ If it generates 1 GJ per day it must also radiate 1 GJ per day... That's a bummer for the requirement that nothing is allowed to leave the dungeon. $\endgroup$
    – AlexP
    Commented Apr 4, 2020 at 18:20
  • 1
    $\begingroup$ It can't be in orbit or on the surface? Do you mean it must be buried? $\endgroup$
    – Matthew
    Commented Apr 4, 2020 at 19:14
  • 1
    $\begingroup$ To clarify, this thing is fragile, right? Otherwise. I would make it thermally resistant and place it inside the sun. Obtaining energy would not be a problem, and if the equipment running it were capable of surviving the time frame, it would be perfectly protected and undetectable by virtually anything. Did anyone read David Brin's Sun Diver? Not a dungeon, though. $\endgroup$
    – DWKraus
    Commented Apr 4, 2020 at 21:50
  • 1
    $\begingroup$ what about deepest underwater? even now people unable to fully explore it compare to space and i think if people manage to achieve that they probably already achieve time machine, or maybe inside jupiter, and i think dont build dungeon just build box or cage to contain the thing and only your Alien key or technology can open it, because dungeon or labyrinth just make people curious and sooner or later will try to explore and easily revealed by satelite or other mapping technology. $\endgroup$
    – Li Jun
    Commented Apr 5, 2020 at 8:13

1 Answer 1


Pando the dungeon tree.

pando the tree



Pando (Latin for "I spread out"), also known as the trembling giant,1[2] is a clonal colony of an individual male quaking aspen (Populus tremuloides) determined to be a single living organism by identical genetic markers[3] and assumed to have one massive underground root system. The plant is located in the Fremont River Ranger District of the Fishlake National Forest at the western edge of the Colorado Plateau in south-central Utah, United States, around 1 mile (1.6 km) southwest of Fish Lake.[4] Pando occupies 43 hectares (106 acres) and is estimated to weigh collectively 6,000,000 kilograms (6,600 short tons),[5] making it the heaviest known organism.[6][7] The root system of Pando, at an estimated 80,000 years old, is among the oldest known living organisms.[8][9]

A thing which must persist and work for so long must be sustained. The easiest way to have a thing be sustained is to have it sustain itself; it is alive. Fortunately the known living thing old enough to meet your needs is also large enough! Your dungeon is a clonal tree, like Pando. At 43 hectares it is well under your size limit. Pando easily generates the power needed for your vase. Additional power will be used to maintain the organism, or will be stored as sugars for dark periods and winter. Pando is 80,000 years old which is well past your 20,000 years required.

Your vase resides in the great dungeon root which Pando maintains in addition to maintaining the clonal forest above.

As regards dungeon creatures they are many and include jays, chipmunks, squirrels, and a porcupine. Sometimes a coyote or bobcat takes up residence. A lake near the dungeon has lake trout, crayfish and muskrat.

If you really need mind flayers and umber hulks I suppose they can live in the dungeon root as long as they take good care of it.


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