Immersive Cities

Githyanki Diaspora had a post titled "Reddit GM Advice: Established Settings, Immersive Cities, and Clues in Investigation Games"

The part that interested me was the Immersive Cities. The basic question is

How do I make a large city experience immersive? What things should I keep in mind given they will only be in this city (initially) for two or three sessions. Should I instead lengthen their stay and make an adventure out of it?

I want to make sure this doesn’t feel like “just another city” for them.

The answers are not bad, but my answer would be different and I don't feel like dealing with Reddit to answer so I'm doing it here. To start I usually give out a map of the city to players, the map includes the main locations they might want to go. So when you read the answers think point-crawl and theater of the mind.

• Mystery. Instead of the normal city map (with legend) provide a city map that only has the legend of a single ward, leaving the rest a mystery until they spend more time in another ward and gradually get to know the city.
• Crowds. If traveling during the day describe the cities open markets and piazas as crowded. Friendly crowd, angry crowd, mix it up. The crowds could be because its just that crowded in the big city, or because some guy is giving a religious rant about the changing color of Cockatrice Eggs over time, who knows, who cares. Describe the players getting jostled by toughs that try to stare them down, and by halflings that might be pickpockets or just innocent jockers. Make them paranoid since these are folks used to living in smaller more controlled settings or in the solitude of the wilderness.
• Festivals. This is the biggie and it goes with crowds. Festivals allow the GM to add some weird fun to the setting. Justifies the crowds. And makes things memorable. IF they have a festival every couple of weeks the players are gonna remember that city. Festivals also includes in a minor way the parade of clergy or nobles or C list celebrities that the population might crowd around to see.
• Lacking solitude. The city is a busting place. If you use long and short rests consider that a short rest takes 8 hours and a long rest is impossible unless they find the right place to sleep. Quiet inns are just to noisy for someone whos ever instinct is spring-loaded for action. Church bells (or whever the fantasy equal is) are just to disturbing. The constant fear of burglars and sceams in the night just make it hard to properly rest unless the players stay in the expensive inn or buy a place of their own. Or they can stay at the slightly more dangerous inn outside the walls.
• Decorum. Most cities are not going to tolerate PCs walking around fully armed and armored. It might not matter in the bad parts of town but where the rich live you better have a reason (such as hired guard for someone). And the PCs better not walk around covered clothes stained in the blood of a thousand foes or city guards will stop them constantly with a ton of questions. This might fly out on the Marchlands where danger is an everyday thing but in the big city, well you can expect the Thieves Guild to report overly armored folks simply to make their own lives a bit safer. This also leads to what is tolerable to wear (Samurai could go about armed but nobody else could) and where do you put your arms and armor so they are safe.

I wouldn't do this in a normal size town but a London, Rome, or Jerusalem... make it stand out. And remember the solitude one can be taken even further. PCs are like war veterans suddenly dumped in a semi-peaceful environment where they can't just kill their problems. The GM should exploit that.