The Sonar data set offers information about mobility exhibited by attendees to the Sonar festival that took place from the 18th to the 20th of June, 2015 in Barcelona, Spain. The Sonar festival is a multistage event with more than 100,000 attendees in two main venues, Sonar by Day and Sonar by Night. We only collected information in the day part from 12:00 to 22:00 in the four simultaneous stages. The data has been anonymized and the location has been reduced to the hall number in order to reduce privacy issues.