Oros is a ruined city in Essos. The city is located at what used to be the meeting point of the Valyrian Peninsula and the Essosi mainland. The area immediately south of Oros was obliterated in the Doom of Valyria four centuries ago, creating the Smoking Sea. The ruins of Tyria lie across the sea to the south.
In the books
In the A Song of Ice and Fire novels, Oros is connected by a Valyrian road to Mantarys. It was located close to the Fourteen Fires, the great volcanic mountain range stretching across the neck of the Valyrian Peninsula. Given its close proximity to the volcanoes, it was likely laid waste during the Doom.
- Oros at A Wiki of Ice and Fire (spoilers from the books)