Let's say there is a city, about the size of New York City, that is made only out of stone, steel, and glass. This city would be completely underwater. Assuming no humans are alive in this city, how many years would it take for the city to be destroyed fully?

(Edit 1) By destroyed fully, I mean so it is unrecognizable as a city but rubble remains.

  • 1
    $\begingroup$ Destroyed - meaning be completely unrecognizable or hidden from sight? The remnants will be there for millions of years. $\endgroup$
    – Alexander
    Jan 19, 2018 at 17:53
  • 5
    $\begingroup$ There was once a city, of which we don't know the name, on the southern coast of the Peloponnese, between the modern islands of Pavlopetri and Elafonisos; it sunk into the sea about 3,000 years ago. It still recognizable as a former city, with paved streets and stone buildings. $\endgroup$
    – AlexP
    Jan 19, 2018 at 17:57
  • 2
    $\begingroup$ What does fully destroyed mean? $\endgroup$
    – sphennings
    Jan 19, 2018 at 18:08
  • $\begingroup$ The rate of "destruction" depends on many factors such as depth, temperature, salinity and water movement. $\endgroup$ Jan 19, 2018 at 21:31
  • 1
    $\begingroup$ I can't answer this without knowing what 'destroyed' means, so I'm voting to close. $\endgroup$
    – kingledion
    Jan 20, 2018 at 3:22

2 Answers 2


If the city is deep enough and the water is still enough that there is no oxygen in the water, there will be minimal decay.

Ottoman ship in Black Sea https://www.nytimes.com/2016/11/12/science/shipwrecks-black-sea-archaeology.html

At the bottom of the Black Sea there is no oxygen. That means no eukaryotic critters and no rust (iron oxide). There is no oxygen because the water is deep and still - so minimal sediment motion and things stay unburied.

The depicted ship is 1000 years old and it has recognizable rope. A structure of steel, glass and stone would persist indefinitely in these conditions.


There's a lot of factors that go into this, not just city size and composition. If the city is in a ocean current, then it'll probably erode faster than if it's in still water. Likewise, the stability of the ground is a major factor. Cities near to tectonic features (such as plate boundaries, volcanoes, etc.) are probably gonna have some issues.

Furthermore, metal erosion is dependent on what's rusting it. I'm not gonna get into chemistry, but some locations will rust faster than others.

But... Where is the boundary for completely destroyed, anyways? Remember that if it isn't destroyed fast enough, then it'll get fossilized and it'll take much longer to be destroyed.

You've gotta keep eldritch effects in mind, too. R'lyeh is an example of a buried city that's under the protection of cthulhu, so it won't erode like a normal city. And Atlantis has its own deity.

In conclusion

The destruction of your city is heavily dependent on where it is and what it's made of.

  • $\begingroup$ So, what you're saying is, the question is too broad. $\endgroup$
    – Spencer
    Jan 20, 2018 at 10:43
  • $\begingroup$ Basically. Now that you say that... I guess I shouldn't have answered it at all. $\endgroup$ Jan 20, 2018 at 17:22

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .