I have a homebrew world and have found lots of tools for wilderness design & encounters, but I'm hazier on urban. Since I'm building my world from scratch, I don't use the published adventures, but I know some of them have excellent descriptions of the various cities of the Realms. For those who use them, which adventure has the best city description that would allow me to look at what they have and use its design as a template for creating my own?

Waterdeep: Dragon Heist is a whole adventure book set in a city. It has tones of resources and descriptions, probably more than you will ever need. 

Waterdeep: Dragon Heist has a good description of Waterdeep
Descent into Avernus describes Baldur's Gate pretty well
Ghosts of Saltmarsh gives a decent description for small towns in the aforementioned Saltmarsh
Guildmaster's Guide to Ravnica is basically one big city description. It almost feels like Sigil from Planescape.
Out of the Abyss has Gracklstugh, Blingdenstone, and Menzoberranzan all in pretty good detail
Wayfinder's Guide to Eberron has Sharn, a magitech city, but I would wait for Last War in case its duplicated there

Other books with city descriptions:
Dungeon of the Mad Mage has Skullport, but its basically just a list of locations

D&D 2e (or even AD&D 2e) had the city of Glantri in the nation by the same name on the planet of Mystara. That’s my favorite pre-built city in all of D&D.

Wow, all the Mystara stuff out there — could help me not just with cities, but the rest of the world. I've done very little on various clans, factions, guild politics, etc. Houligan's point about Ravnica is worthwhile — hadn't even thought about that, which I already have since I recently bought the Source Bundle, but it's almost too much — too big to emulate, but still ideas to pull from it. Definitely going to spend some time digging through Mystara, especially Glantri, and Waterdeep sounds great for big cities & Saltmarsh for smaller.

Thanks to all for your input.

Unfortunately, the only book in the source bundle with good descriptions is the Ravnica one. Everything else is in an adventure.

Edit: and Sharn in Wayfinder's Guide

Yeah, I'm willing to buy an adventure or 2 just for the source material. I notice the Mystara PDF is also available @ Drive-thru RPG.

You can probably find the AD&D “Glantri: Kingdom of Magic” campaign setting box online somewhere. It comes with a full campaign setting, maps for both country and city, pre-written adventures (some better written than others) and best of all none of your players are likely to recognize anything you “borrowed” from something that was published over 20 years ago. ;) The city map and campaign setting materials alone are worth it for a fantastic Venetian feeling city.