He showed off his muscles in Troy this summer, but Brad Pitt likes to remind folks that there's more to him than just good pecs. On Nov. 1 he quietly paid a visit to former South African president Nelson Mandela, 86, in Johannesburg. Brought along by his friend, Virgin CEO Richard Branson—wife Jennifer Aniston was home in Hollywood—they discussed Mandela's 46664 campaign (named for his prison ID number) to call attention to South Africa's devastating AIDS epidemic (other celebrities pitching in have included Will Smith and Beyoncé Knowles). "Brad was fantastic," says Branson, who invited Pitt, 40, on a weeklong trip to Africa—the actor's first—that also promoted the airline founder's campaign to clear land mines. "He's passionate about these things and wants to learn." In fact, Pitt has been applying himself to all sorts of big topics lately: He campaigned for John Kerry before the election and spoke in support of stem-cell research. An architecture enthusiast, he has also become pals with Dutch designer Rem Koolhaas.

After meeting Mandela, Pitt visited AIDS clinics in Johannesburg, motorbiked to a lodge in nearby Clarens, then flew to Ethiopia on behalf of DATA, a third-world lobby group cofounded by U2's Bono. "I've spent a wonderful week traveling this beautiful continent," Pitt said in a statement, "listening to the people and learning about the AIDS crisis, the extreme poverty and what people in America can do to help."