Long after a war that wipes everything out the society in the story worships (?) a huge monolith. Their attempts to open it fail. Part of the monolith opens and a huge round device unfolds. The citizens climb it and examine it but cannot do more as it is so huge. At the end it is revealed a recorded voice is calling out to only press the button if the world is now safe for humans to survive again. Inside the monolith are humans in suspended animation. And that the citizens are ants and cannot hear…
I remember that story. Just not anything useful.
Paging @Andy_L
Sounds like part of Clifford Simak’s City future history. Not from the fix up novel but maybe an earlier short story.
The voice from the curious cube by Nelson Bond.
It does sound like “Epilogue” the last City story (not included in early versions of the book)
In too late-I read that story in Asimov’s Short Short Science Fiction collection.