Described variously as a single Mount Qaf that serves as the progenitor of all mountains, or as a ring of soaring mountains that encircle the world, the mountains of Qaf, or Jabal al Qaf in Arabic, are often described as the home of the Jinn.
The mountains may have a giant emerald at the summit, or be comprised entirely of emerald or the green stone periodot. The sky above them is tinted green from the jewels below them. It's less clear what's beyond the mountains of Qaf. It could be more peaks battered by snow and hail which can cool the fires of hell itself, or vast plains of gold inhabited by angels.
In the Persian tradition, entire cities of supernatural creatures comprise a state entity known as Jinnestan. The Peri, who resemble the fairies of Western folklore, inhabit cities of multi-colored jewels and amber while their demonic arch-enemies the Dev inhabit a sprawling metropolis overseen by an enchanted castle.
Unless I can figure out how to shrink myself into a magical oil lamp, I might not be traveling to the Mountains of Qaf anytime soon. But if I could I'd fly there in a heartbeat...
References: Legends of the Fire Spirits by Robert Lebling, The Adventures of Hatim Tai: A Romance, Janardhan Ramachandraraji