This paper describes an exploratory study on group interaction with a robot guide in an open largescale busy environment. For an entire week, a humanoid robot was deployed in the popular Cosmocaixa Science Museum in Barcelona and guided hundreds of people through the museum facilities. The main goal of this experience is to study in the wild the episodes of the robot guiding visitors to a requested destination focusing on the group behavior during displacement. The walking behaviorfollow-me and the face-to-face communication in a populated environment are analyzed in terms of guide–visitors interaction, grouping patterns and spatial formations. Results from observational data show that the space con¯gurations spontaneously formed by the robot guide and visitors walking together did not always meet the robot communicative and navigational requirements for successful guidance. Therefore, additional verbal and nonverbal rompts must be considered to regulate e®ectively the walking ogether and follow-me behaviors. Finally, we discuss lessons learned and recommendations for robot's spatial behavior in dense crowded scenarios.