The development of sustainable urban projects is crucial to address the challenges of the growing population living in cities. Facing complex decision-making and increasing expectations from inhabitants, local institutions are gradually becoming open to co-design urban solutions with the population. However, adequate dwellers' mobilization is complex to implement. For more than 20 years, through the development of civic technologies, digital solutions have been increasingly adopted in urban participatory approaches. These modern methods aim to facilitate the dialogue between the citizens and the institutions; however, the currently implemented approaches still remain limited. In this thesis, I explore the opportunities of digital 3D (such as virtual geographic environments) in urban participatory e-planning in light of four outlooks: the current practices, the participants, the 3D medium, and the future practices. The findings demonstrate that typical digital participatory settings do not stimulate the active engagement of the population. Therefore, I suggest a set of recommendations that would improve the design and use of 3D tools, hence enhancing participatory approaches. The design guidelines, articulated around customization and the creation of affordances, are discussed through the implementation of successive 3D participatory prototypes and assessed by local authorities and urban experts. This research, addressed to practitioners, officials, experts, and fellow researchers delivers crucial insights to enhance the design of 3D participatory tools, which leads to more inclusive approaches, an improved legitimacy of decision-making, and ultimately drives to a better, more sustainable development of cities.