BioBlitzBcn is an exhaustive and collaborative census of the biological species at Barcelona city. Typically performed in urban parks, this initiative involves school students, volunteers and other participants guided by scientists to explore, discover nature and count the biodiverisyt in a race against time. Since 2010, Barcelona has organized an annual BioBlitz in which more than 5,000 people have already participated and close to 3,000 species have been identified.