Corsica

The mountainous island in the Tyrrhenian Sea where Claudius banished Seneca for eight years on a charge almost certainly invented.

Corsica was a place Rome sent people to forget them. Seneca arrived in 41 CE accused of adultery with the emperor's niece, and stayed eight years on an island he described as barren rock without fruit, water or civilised company. The description says more about his misery than about Corsica. He wrote consolations from there, including one to his mother and one to an imperial freedman that reads like a job application. It worked, and Agrippina had him recalled to tutor her son Nero.