The Poet's Star Guide: A Planeswalker's inquiry into Philosophy...
Major planar passageways that connect to Arborea include the River Oceanus, River Jordan, Mount Olympus, Yggdrasil, and Xibalba (which sometimes referred to as Mictlan, but Mictlan is now just a place in the Grey Wastes of Hades). Also, Arborea contains one nonplanebound realm, the Seelie Court, or the Summer Court.
The first layer contains the following independent towns: Thrassos, Here Be Monsters, and Freedom of Speech. The first layer also contains the following sites: The Gilded Hall and the River Achelous. And the first layer is home to the following realms: Arvandor, Brightwater, Loom of the Celestial River, Florallium, Olympus, Whistledge, Uden, Joys Unforgotten, Fermata, The Absorbing Light, Songsheight, and The Forking Road.
The second layer contains the following independent towns: Elshava and Hope of a Better Tomorrow. The second layer also contains the following sites: Mount Ossa and Mount Aetna. And the second layer is home to the following realms: Caletto, Elavandor, and The Primeval Abyssal.