To make a long story short, every time the adventurers go from one neighborhood or sector to another, or every hour they spend in the streets, the referee must make an encounter roll, and if an encounter occurs, she must use a table designed specifically for the city, or she can use Chris Gonnerman’s table in Basic Fantasy RPG (p. 146).
Each city has at least one point of interest that can be turned into an adventure. These places must be actively sought, but can also be found randomly, if included in the encounter table: Normally the graveyard is a quiet space, but some nights (perhaps an encounter roll is required) it is possible to see dark shadows inside. The inhabitants prefer to ignore them, but if the adventurers decide to poke their noses in, what will they find? Looters? Body snatchers? Anthropophaghoul? The monks of the monastery engaged in, ahem, illicit activities? These kinds of encounters must be planned in advance, perhaps foreshadowed on your rumors table.
There, that’s it.
Normally, an encounter occurs on a result of 1 on a d6, but this probability may be higher at night or in cities of high danger.
In a densely populated city, where the neighborhoods are of considerable size, two or even three encounter rolls can be made every hour.
An adventure starts when there is something at stake. If the adventurers are simply looking for supplies and lodging, the encounter roll should be omitted, especially if they are not interested in having adventures right now.
If they seek refuge and are being chased by the town guard, that’s an adventure.
If the adventurers ask a villager where they can find a cheese wheel, the villager will give them directions, and it’s not an adventure. If they don’t ask and decide to explore the town, then it’s probably an adventure.
The first time they visit an unfamiliar city, it may be an adventure.
Villages and shantytowns don’t have a neighborhood structure, but it’s easy to divide them into two, three or four parts, just for the purpose of running an adventure.