Cutting a solitary figure in his four star general's uniform, Cuban President Raul Castro placed a cedar box containing his brother's cremated remains in a niche in the rock at the Santa Ifigenia Cemetery in southeastern Cuba.
A dark plaque engraved with the word "Fidel" was then fixed over the niche. Raul Castro saluted the rock, which was flanked by two honor guards in white uniform, and a 21-gun salute echoed out.
Fidel Castro toppled a U.S.-backed strongman in a 1959 revolution and went on to build a Communist state a short distance from the Florida coast, surviving the collapse of the Soviet Union and relentless U.S. efforts to force him out.
His monument at the cemetery in the city of Santiago de Cuba sits a few steps from the mausoleum of independence hero Jose Marti, another towering figure of Cuban history with whom Castro shared a mistrust of the United States.
Castro's naturalistic memorial is dwarfed by Marti's mausoleum and other elaborate edifices at the cemetery.
The stone is a few steps from a monument to rebels who died in an attack on the Moncada military barracks in Santiago at the start of the revolution.
Since Castro's death on Nov. 25 at age 90, hundreds of thousands of Cubans have lined streets and plazas to bid farewell to "El Comandante" (The Commander), with a combination of tears, vows to sustain socialism and choruses of "I am Fidel!"
By contrast, the ceremony on Sunday was a private event and not broadcast on state media.
A few photos and eyewitness accounts on state media described a small group of guests including Castro's wife Dalia Soto del Valle and Argentine soccer legend Diego Maradona, who was a friend of the Cuban leader.
A clutch of left-wing allies were also present, such as Nicaraguan President Daniel Ortega, who like Castro survived the Cold War.
Later, members of the public were allowed to lay flowers at the memorial in small groups of ten.
"I wanted to give him one last goodbye, although he will always be present in my heart," said Angela Rodriguez, 62, one of the first people allowed to view the boulder.