Isso é quase definitivamente Ringworld de Larry Niven.
A montanha em questão parece estranha para Louis e companhia porque é muito grande e está localizada no meio do ringue, enquanto a maioria das montanhas faz parte do ringwall.
"That's the biggest tanj mountain I ever saw in my life."
"Louis!"
He had spoken too softly. "A mountain!" he bellowed. "Wait'll you see it! The Ringworld engineers must have wanted to put one big mountain in the world, one mountain too big to use. Too big to grow coffee on, or trees, too big even for skiing. It's magnificent!"
It was magnificent. One mountain, roughly conical, all alone, forming no part of a chain. It had the look of a volcano, a mock-volcano, for beneath the Ringworld there was no magma to form volcanos. Its base was lost in mist. Its higher slopes showed clear through what must be thinning air, and its peak had a shiny look of snow: dirty snow, not bright enough to be clean snow. Perhaps permafrost.
There was a crystal clarity to the edges of the peak. Could it thrust clear out of the atmosphere? A real mountain that size would collapse of its own weight; but this mountain would be a mere shell of ring foundation material.
Louis percebe o que é Punho de Deus (o que os nativos chamam de montanha), mas se recusa a dizer isso em voz alta, porque ele não corre o risco de parecer tolo até o momento em que chega ao topo.
"Remember the night you explored a giant map of the Ringworld? You couldn't find Fist-of-God. Why not?"
The kzin didn't answer.
"It wasn't there, that's why not. It wasn't there when the map was made."
[...]
"Louis, just what do you expect to find in Fist-of-God crater?"
"Stars," said Louis Wa.
The kzin was tense too. "Do not mock me! In all honor---"
---And they were through. There wasn't any pass. There was only a broken eggshell of Ringworld foundation material, stretched by terrific stresses to a few feet of thickness; and beyond that, the crater in Fist-of-God Mountain.
They were falling. And the crater was full of stars.
Parece haver um pouco de confusão quanto à estrutura; em resumo Ringworld é uma megaestrutura de aproximadamente 300 milhões de quilômetros (300 Gm) de diâmetro (950 milhões de quilômetros em circunferência) e cerca de 1.6 milhões de quilômetros (1.6 Gm) de largura. É relativamente fino, da ordem de 10s de km de espessura, e gira em torno de sua estrela central para produzir em torno de 1g de pseudogravidade. Milênios antes da história, um planetoide desonesto interestelar do tamanho da lua o lado externo do anel em velocidade.