Does Jules Verne ever say where the Nautilus was built or constructed? Maybe in another book that I have not read the location is stated.
Its parts are built to order in France, the United Kingdom, Krupp of Prussia, Sweden, the United States, and elsewhere. Then they are assembled by Nemo's men on a desert island. Nautilus most likely returned to this island and later helped castaways in the novel The Mysterious Island. After Nemo dies on board, the volcanic island erupts, entombing the Captain and Nautilus for eternity.