Over 60,000 Pay Tribute to Mandela in JohannesburgMore than 60,000 people converged at FNB Stadium in Johannesburg on Tuesday for a memorial service to honor the late South African President Nelson Mandela. A steady rain did not stop mourners from singing and dancing in tribute to Mandela, as speakers praised him for his role in ending apartheid and healing South Africa's racial divisions. U.S. President Barack Obama called Mr. Mandela "a giant of history, who moved a nation toward justice, and in the process moved billions around the world." U.S. President Barack Obama addresses the crowd during a memorial service for Nelson Mandela at FNB Stadium in Johannesburg, Dec. 10, 2013. “Over thirty years ago, while still a student, I learned of Mandela and the struggles in this land. It stirred something in me. It woke me up to my responsibilities - to others, and to myself - and set me on an improbable journey that finds me here today. And while I will always fall short of Madiba’s example, he makes me want to be better. He speaks to what is best inside us. After this great liberator is laid to rest; when we have returned to our cities and villages, and rejoined our daily routines, let us search then for his strength -- for his largeness of spirit -- somewhere inside ourselves," he said. Earlier, U.N. Secretary-General Ban Ki-moon said the world has lost a hero, a father, a friend and a mentor. In his keynote address, President Jacob Zuma, who was booed twice at the stadium, said Mr. Mandela was a unifier. U.S. President Barack Obama greets Cuban President Raul Castro at memorial service for late South African President Nelson Mandela, Johannesburg, Dec. 10, 2013. Other speakers included Cuban President Raul Castro and Brazilian President Dilma Rousseff, who praised Mandela for his role in dismantling the apartheid regime. Political analyst and former Zimbabwe student leader, Paul Chimhosva, now project manager at EXXARO Resources in South Africa, said even in death Mr. Mandela continued to unite people as was seen in the handshake between President Obama and Cuban leader Castro at the memorial service. Mandela became South Africa's first black president in 1994, after being imprisoned for 27 years for his role in the struggle against white minority rule. Along with President Obama, the U.S. delegation included first lady Michelle Obama and former Presidents George W. Bush, Bill Clinton and Jimmy Carter. George H.W. Bush is the only living former U.S. president who did not attend the event. His spokesman said the 89-year-old Mr. Bush is no longer able to travel long distances. A man kisses the portrait of South African former president Nelson Mandela during his memorial service at the FNB Stadium (Soccer City) in Johannesburg on December 10, 2013. Mandela's remains will lie in state at the Union Buildings in Pretoria - the official seat of the South African government - on Wednesday, Thursday and Friday. The memorials and events will culminate in Mr. Mandela's burial on December 15 in his boyhood home village of Qunu. The venue on Tuesday was also the place where Mr. Mandela made his last public appearance at the closing ceremony of the first-ever World Cup in Africa. Madiba, as he was affectionately known, is admired in South Africa and around the world for leading the intense struggle to end South Africa’s racist apartheid regime. He spent 27 years in prison for his opposition to the regime, and emerged to become South Africa’s first black president in 1994. What truly makes him extraordinary was his transformation during those decades in prison from an angry youth leader to a wise statesman who stressed the need for racial reconciliation in this deeply divided nation.