Nisyros, also referred to as the Angry Caldera of Arges, is a Greek volcanic island located in the Aegean Sea, east of Anaphi and south of Kos. Together with Anaphi and Thera, Nisyros formed the Greek region called the Volcanic Islands.
Around 420s BCE, the island was desolate and uninhabited, but remains of Isu architecture littered the ground. In the middle of the island was a natural arena, surrounded by lava. Between 429 and 422 BCE, the Spartan misthios Kassandra visited the island and eliminated Arges, claiming a hammer which had allegedly been forged by the Isu Hephaistos.