Huh, yeah, I'm surprised I've never heard of it then.
Now Myth Drannor, on the other hand, I know quite well
Well Mulhorand was popular enough when they blew it up 4e, that FR fan outrage made WotC being the nation back in 5e.
And Skuld was its Capital where the Gods held their Palaces, where the Pharoh and the God Kings dwelled.
Skuld had a population of over 200,000 in some sources, although originally it was 92,000. (Mulhorand had a population of over 5,000,000, 2% of which were planetouched and 2% half orcs, the rest humans in 3e).
It had Catacombs under the city that were infested with Werecrocodiles and other monsters.
I think it didn't get as well known outside of hardcore FR fans because the original author made it specifically hostile to adventurers in the sense of fees, permits, and liciences for weapons, spells, and Elves. I think for 5e I'd do away with with stuff like that, the nation of Mulhorand is in a phase of renewel and opportunity where before they were in a phase of decline and decay before disaster in 4e.
I wish they'd do more with the Old Empires region, its one of the less generic regions capared to the Sword Coast and the North.
Personally for me the more generic regions are the Sword Coast and the North (not including the isles), the Heartlands, and the Moonsea.
The less generic regions are the Old Empires, Lands of Intrigue, Unapproachable East, Shining Sea, Cold Lands.
The thing is is that the Forgotten Realms is a setting of settings. You have the big ones in Al Qadim, Maztica, Kara Tur, and arguably the world of Abeir, then you have smaller settings in areas like the Old Empires region, Unapproachable East, the Cold Lands, ect..., all with their own themes, but all interacting.
So each of these subsettings have their own Iconic cities.
And yeah Myth Drannor is fameous as both dungeon and city.