Thousands of Cubans lined up at dawn carrying portraits, flowers and flags to pay their respects to Fidel Castro.
The mourners were seeking to bid farewell to the man who ruled the country for nearly half a century.
One of the first in line was Tania Jimenez, 53, a mathematician who arrived at 4 a.m. carrying a rose.
"Fidel is everything to us, the soul of this country who gave everything, all his life," Jimenez said in tears.
A nine-story image of a young Castro joined the towering images of fallen guerrillas overlooking the massive square where the government said Cubans would "render homage and sign a solemn oath to carry out the concept of the revolutionary expressed by the revolutionary leader."
Castro was cremated Saturday and the government has declared a nine-day period of mourning.
His ashes will be carried to a final resting place in Santiago de Cuba, the city in eastern Cuba where he launched the revolution.
Monday's mourning began with a thunderous cannon salute that could be heard throughout much of the capital at 9 a.m.
Mourners paraded past a photo of a young Castro dressed in military fatigues, gazing into the distance with a rifle and pack slug over his back. A military honor guard and some civilians flanked the photo and an arrangement of white flowers.
Among them was Ana Maria Vazquez, 49, who said she once worked in Castro's office in the Council of State.
"Fidel was country. He was revolution. But above all Fidel was a man who opened his heart to the people," said Vazquez, wiping away tears.
Political opponents stayed away or kept quiet, allowing admirers to say goodbye to a man who elevated the island to the world stage during the Cold War by forging a communist-run state just 90 miles from Florida and then resisting Washington's long efforts to force change.
"He wasn't perfect. Nobody is," said Roberto Videax, a 72-year-old retiree who was nonetheless proud of Castro. "Fidel was a teacher, a patriot."
The ceremony in the capital will end Tuesday night when foreign leaders are expected to pay their respects.