After presenting the agents, let’s identify the scenario of density, which is the city.

When we talk about city we indentify its elements in two superimposed layers: fluxes and space. There are different types of fluxes:

- Natural fluxes (the climate system): the dynamics which affect the ecosystem of a given space, such as the rivers, the sunlight...

- Virtual fluxes, which are driving forces to which the ownership and management of the space is related, such as business fluxes, political decisions, social trends...

- Physical fluxes of people and goods which describe human activity.

As a result of theses fluxes, the space is divided into solids and voids.