The two couples took a boat to the event, which was being held near the Hollywood star's fancy digs.
The foundation, founded by George and Amal, is aimed to help marginalized communities that have experienced human rights violations.
The former President and First Lady kicked off their travels in France. They spent time with U2's Bono and The Edge on the French Riviera before heading down to Italy. They are slated to return home to the United States on Monday, June 24.
Barack and George have been friends for years. The Ocean's Eleven star was one of Barack's most outspoken supporters during his time in office.
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