I give my players a blank map of the town, which they can gradually fill in during their adventures. The map is accurate in a big picture sense, but may not include every small alley, house and courtyard. In our current campaign, the largest town looks like this:
When the players want to move through town, I ask them to describe which route they are taking, and roll random encounters / insert planned ones as they go. For example (from our last session):
PC: We need to go to the houndmonger now. The knights of Yolanthus Kar will seal up that opening if they discover it first.
GM: Which way are you going? You are still at
The Murk. It is late afternoon, fishing boats are pulling into the harbour, and sailors are looking for places to get drunk."
PC: We go around - along the harbour to the Golden Plate, to the market, then across the bridge and southwest into the eastern part of town. The peddler told us the dog pound is near the Masters' Guild.
GM: <rolls random encounter on a 1:6> You round the harbour. There is a lot of foot traffic, and revellers are all around you.
PC: We watch for pickpockets.
GM: <rolls to see just in case, but nobody makes a try; then rolls a random encounter, coming up at nothing> The market is almost deserted except for the beggars congregating around a pillar with a statue on top of it, and music coming from the upper terrace of The Nine Doors.
GM: ...you continue, and arrive in the poorer part of town. Lanterns are being lit everywhere as dusk falls, and drunks stagger to their favourite haunts.
PC: Do we see that strange guy we saw last time in that doorway?
GM: Nope, you take the same route, but he isn't there now. ... <rolls> You pass a dirty dive with open doors and sounds of a fiddle coming from inside. A bunch of orcs are celebrating and drinking, and two of them are outside, one supporting the other as he disgorges his former meal.
PC: Nope, not getting involved. We continue.
GM: You leave behind the pub and its last pool of light. You pass by the Masters' Guild with its shuttered stores and crumbling parapets. These streets are empty and dark, with side alleys leading off in unknown directions.
PC: The dog pound should be north from here. We go that way.
GM: The dagger from above comes without a warning or announcement. <rolls to hit> It misses Armand the Scumbag and clatters harmlessly on the pavement. What do you do?
And so on. I have my own (fairly detailed) city encounter system that breaks down encounters by day/night and quarter (Noble, Bazaar, Harbour and Thieves'). For really large cities, I also use Mythmere's
City Encounters, and
The Nocturnal Table, its companion volume I wrote for Knockspell, but which remains unpublished.
This is the closest I have been to running a citycrawl; it is basically a pointcrawl without exactly defined points, and high transparency on the players' side. I would love to see a good system for running something in the vein of
Khare: Cityport of Traps or
City of Thieves, but don't know an appropriate system of procedures which could handle it (it would also be a lot of work to go from abstraction to full detail). I guess it could be done with something on the level of
City State of the Invincible Overlord.