In what city was a baby secretly set on fire each night?

The correct answer is Eleusis. In historical and mythological contexts, Eleusis is significant for its association with the Eleusinian Mysteries, ancient religious rites held in honor of Demeter and Persephone. These mysteries involved various rituals that were fundamental to the cultural and spiritual life of ancient Greece.

The mention of a baby being set on fire each night refers to a ritualistic practice possibly linked to agricultural cycles, symbolizing death and rebirth, where the baby might represent new seeds or the cycle of fertility. Eleusis, being a prominent site for such rituals, is closely associated with these themes, reflecting the ancient Greeks' reverence for the life-death-rebirth cycle in agriculture and mythology.

Other cities listed, such as Athens, Rome, and Corinth, do have historical importance but are not specifically connected to the described ritual of a baby being set ablaze each night within the context of the Eleusinian mysteries or similar traditions.