City of Brass
The City of Brass is a location in the Dungeons & Dragons multiverse; this enormous city is found on The Plane of Fire in the Great Wheel or the Elemental Chaos in the World Axis. It is the foundation of the empire of the efreeti, a race of fire-aligned genies, and is the center of their power in the multiverse. This is often a place where adventurers will go to find magic items, as for some reason they have a ton of them.
Unusually for a planar location, which Wizards normally guarded with jealous attention, the City of Brass also exists in Pathfinder, and also on its Plane of Fire. This is likely due to name originating in One Thousand and One Nights, rendering it impossible for Wizards to acquire a broad trademark on, and a stray reference in the text for Unearthed Arcana, which was released under the Open Gaming License, mentioning a visit to "the City of Brass where they must bargain with an efreeti lord". Likewise, it's a hub for interplanar trade.
In Pathfinder
In the Pathfinder setting, the City of Brass featured prominently in the Legacy of Fire adventure path, where the PCs are trapped in an enemy fortress within the city and are tasked with recovering an artifact known as the Impossible Eye. A unique feature is that the foundations of the city are living brass, a metal created from the souls of mortals who made terribly-worded Wishes. The city is ruled by a tyrannical grand sultan, but his vizier holds just as much power unofficially and the two spent lifetimes scheming to upend each other.
In Al-Qadim
Secrets of the Lamp was the genie-centric sourcebook for Al-Qadim, and as such it detailed the city along with an adventure set within. It is much more martial in nature, where districts are set up as military zones and colonies are maintained all around the Elemental Plane of Fire.
In the Lost Lands (Frog God Games)
The City of Brass in Frog God Games' (formerly Necromancer Games) Lost Lands Setting has more overtly Islamic and Arabian backstory, where the city was originally a multi-cultural creation for the gods' children but the efreeti wanted it for themselves. They were cursed by Sulemein for this transgression, and the Grand Sultan seeks to avenge this dishonor and claim the legacy of godhood. Is notable in that the city is not in the Elemental Plane of Fire, but rather in a demiplane of its own sitting at a crossroads between the non-water Elemental Planes. Originally available for 3rd Edition D&D, a KickStarter updated the book for 5th Edition and Swords & Wizardry along with a full level 1-20 adventure path.