Thousands gathered to celebrate the life and legacy of Nelson Mandela during a memorial service held in Soccer City in Johannesburg. Interestingly, the stadium was also the place where Madiba made his last public appearance during the World Cup in 2010. Over 60 heads of state were in attendance. As were celebrities and international dignitaries. During his eulogy, President Barack Obama called Madiba the "last great liberator of the 20th Century." Here's a look at how the world said goodbye.