(CNN) -- Four past or present United States presidents are among the nearly 100 world leaders joining celebrities and tens of thousands of South Africans to celebrate the life of Nelson Mandela Tuesday -- but some of the world's best-known leaders are not there.
Some are staying home for health reasons, like Queen Elizabeth II and former Cuban President Fidel Castro.
Pope Francis isn't coming because of protocol -- popes simply don't attend the funerals of world leaders.
The situation with the Dalai Lama is a little more tricky.
The Tibetan spiritual leader -- who is a Nobel Peace Prize laureate, as is Mandela -- was not granted a visa to visit South Africa the last two times he applied, likely because of pressure from China.
He last tried to visit in 2011, for the 80th birthday celebrations of Desmond Tutu.
The South African archbishop lashed out at his government for failing to grant the Dalai Lama permission to enter, comparing it to the apartheid regime he and Mandela worked to overturn.
And the Dalai Lama predicted that, denied the visa, he would never see Mandela again.
The Tibetan said at the time he was "very much hoping to see Nelson Mandela, (who is) now very old. Now I have doubt whether I will have the occasion to meet Nelson Mandela or not."
Israeli Prime Minister Benjamin Netanyahu is staying away, officially, for more prosaic reasons -- his office cited the cost of the trip and the difficulty of organizing security on such short notice.
A delegation headed by Knesset Speaker Yuli Edelstein will stand in for the Israeli leader. Likewise, Prince Charles of Wales will formally represent the Queen and Cardinal Peter Turkson of Ghana attends on behalf of the Pope.
Mandela, the former South African president and 1993 Nobel Peace Prize laureate, died Thursday at the age of 95.
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