In the last public event of his three-day visit to the island, Pope Benedict XVI called on Cuba, and the world, to change and choose a path of "love, reconciliation and brotherhood."
After the Mass, the pontiff met with Fidel Castro for a half-hour before departing for Rome, wrapping up a weeklong trip to Mexico and Cuba.
The pope did not meet with Cuban dissidents during his trip, however, drawing criticism from Castro opponents in Cuba and abroad.
The site where the pope delivered Wednesday's Mass — Havana's Plaza of the Revolution — is the same place where Castro, the retired but still influential Communist revolutionary leader, delivered countless speeches over the decades.
The scene Wednesday morning felt somewhat like a political rally — though instead of "Revolution" or "Socialism or Death," the huge banners draped from government buildings carried messages such as "Jesus of Mary" and "Charity Unites Us."
The police presence was heavy and seemed to weigh on the event. It was a sign authorities wanted to keep a tight lid on the proceedings and make sure there weren't any protests or other disturbances by government opponents.
Benedict arrived at the plaza waving from his white popemobile and split the crowd as he headed to a custom-built stage.
Reading from his homily in Spanish, Benedict urged Cubans to find truth in God and freedom in the path of Jesus Christ. He also encouraged the Cuban government to strengthen protections for religious freedoms on the island, saying it establishes solid foundations for the rights of future generations.
"The right to freedom of religion, both in its private and public dimension, manifests the unity of the human being, who is at once a citizen and a believer," Benedict said.
If critics of the Castro government were looking for a more direct challenge to Cuba's one-party state and a push for greater political freedoms, Benedict did not deliver. To form a more worthy and free nation, he said, quoting from 19th-century Cuban priest Felix Varela, the island needs a deeper spiritual life.
"Cuba and the world need change," Benedict said, "but this will occur only if each one is in a position to seek the truth and choose the way of love, sowing reconciliation and brotherhood."
Wednesday's crowd was estimated in the hundreds of thousands but felt small for a typical Cuban mass rally. The government had declared a national holiday and encouraged many workers to attend.
For both Cuban President Raul Castro and the Catholic Church, Benedict's visit seemed like a success, finding common ground in a message of anti-consumerism, Cuban unity and gradual reform.
Alexander Espinosa, a devout 24-year-old, had traveled from one end of the island to the other to attend all of Benedict's public events.
"To me Benedict's message has been very clear," Espinosa said. "It's for Cuba's youth to carry on Pope John Paul II's legacy, and to lead this society forward."
Few in the crowd seemed to hear an especially political message in Benedict's visit, and it's unclear if he'll leave the kind of lasting impression with believers and nonbelievers that his predecessor, John Paul II, did in his 1998 visit. Mary Martinez, 60, said for her, Benedict's words were spiritual.
"A message of peace and love," Martinez said. "That's it."