In PRPG2
An island in the Ocean of Dreams. It is inhabited by a violently isolationist colony of ponies founded in the Dark Age; the principle settlement is Martingale's Haven.
In PRPG3
The island has opened up somewhat and is better known now due to census efforts by the Oneiric Curacy, although the population is generally still very much isolationist and visiting outsiders are likely to be treated coldly.