Pop star Madonna, performing Saturday night at a massive free concert at Copacabana Beach in Rio de Janeiro, Brazil.

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Pop star Madonna, performing Saturday night at a massive free concert at Copacabana Beach in Rio de Janeiro, Brazil. / AFP via Getty Images

Madonna capped off her "Celebration" tour with a trip to the beach: Rio de Janeiro's famed Copacabana Beach, to be exact, where on Saturday night she put on a massive free show for some 1.6 million fans. It was the last performance during her globe-trotting retrospective tour as well as her only "Celebration" date in South America — and it garnered the biggest live crowd of her career.

The 1.6 million estimate came from Riotur, the city's official tourism agency. Madonna, who had not performed in Brazil since 2012, enthused about the evening on Instagram: "Words cannot express my gratitude!" she wrote in a caption to a drone video showing the beachfront crammed with fans. As with other "Celebration" shows, she invited local stars onstage with her: In Rio, her guests were Brazilian performers Anitta and Pabllo Vittar, the latter helping Madonna shift her track "Music" into a samba.

Copacabana Beach has something of a history when it comes to huge pop spectacles: In 2006, The Rolling Stones played for an estimated 1.5 million fans there, while a 1994 New Year's Eve show with Rod Stewart reportedly drew some 4.2 million attendees.