Museums' mission statements are changing. Besides preserving, displaying, and disseminating outstanding works of art, history and science, they also need to be open spaces of participation; to be a modern agora that welcomes their community and encourages dialogue.

The Web 2.0 allowed people to actively engage in participatory learning and entertainment, and increasingly, more people want to do more than passively consume information. Peer recommendation has become the primary source in the decision making process, instead of professional reviews and paid advertisement.

While different sectors have long embraced this revolution (Wikipedia, blog publishing, Amazon and Yelp reviews), there was a need to create a participatory platform for museums: a virtual space where museum visitors can share their experiences and knowledge.

Unique Visitors is a result of three years of conceptualization and prototyping. Its development follows user centered methodologies (design thinking, fast prototype, agile development). Every iteration was tested, analyzed, and improved according to visitors' needs and responses. Our goal was to create a useful platform that facilitates participation.

In its third and final iteration, Unique Visitors is a participatory platform where museum visitors can be the curator and create their own tour guides inside the museum collection. It was published in the beginning of 2016, in collaboration with the Museu Nacional d’Art de Catalunya.

In this paper we will talk about what we’ve learned in the previous iterations, our current metrics, and what strategies were more successful in order to achieve visitors' participation.