skylineEngine: An urban procedural modelling system
skylineEngine is an urban procedural modelling tool developed as a test-bed for new algorithms and techniques in urban modelling. It has many features only available on high-end commercial modelling systems, as well as some novel features that make it a unique system, like a graph-based paradigm that allows the user to create contentrich cities with distinct districts, major and minor roads, blocks, lots and buildings, and also other urban elements like streets, sidewalks, parks, bridges and landmarks.

More info: skylineEngine
Raccolet example
Procedural bridges