Eidolon, a Shadow World module provides a city and some excellent settings for politics, gangs, crime and romance. The canals are great for smugglers and the like.
Tharbad City of Thieves was a great city setting in northern Arnor. It too has a river/canal.
Umbar is another great city setting, also in middle earth. The six lords that run the city are particularly good for intrigue and danger. Politics and romance too. A river and the sea here. Water is always great for adventure.
Romance. Love interest have families. A black sheep of the family could be a highway man, a conman, a gang member, a smuggler and many other possible adventure hooks. Of course some may be merchants or doctors or some other nice advantage the party can use. Love interest can be defended. They can also betray.
Rival business and Political factions. All will have their own goons and some may hire criminals or have underworld contacts.
Organized crime and gangs. A must.