“I can see, Captain, that nature is your obedient servant, any time or any place. You’re safe on this lake, and nobody else can visit its waters. But what’s the purpose of this refuge? The Nautilus doesn’t need a harbor.” “No, professor, but it needs electricity to run, batteries to generate its electricity, sodium to feed its batteries, coal to make its sodium, and coalfields from which to dig its coal. Now then, right at this spot the sea covers entire forests that sank underwater in prehistoric times; today, turned to stone, transformed into carbon fuel, they offer me inexhaustible coal mines.”

— Twenty Thousand Leagues Under the Sea (Extraordinary Voyages, #6) by Jules Verne