In a sometimes comic, sometimes tetchy press conference - which in an extremely rare move was carried live on Cuban television - Castro refused even to acknowledge that his government holds political prisoners. "After this meeting is over, you can give me a list of political prisoners, and if we have those political prisoners, they will all released before the night ends," he said in a sarcasm-laden response to a US journalist's question.
However, the mere fact that the joint press conference took place in Havana's Palace of the Revolution - after the leaders met for more than two hours - demonstrated how much has changed. Obama, the first US president to visit Cuba in 88 years, hailed a "new day" - a "nuevo dia," as he said - in relations between the former Cold War foes.
And Castro suggested the former enemies take inspiration from US endurance swimmer Diana Nyad, who in 2013 managed on her fifth attempt to become the first person to swim from Cuba to Florida without a shark cage. "If she can do it, we can do it too," Castro told journalists after the leaders met in the palace - the nerve center of the communist government that has ruled Cuba since the take-over by Raul's brother Fidel Castro in 1959. Trying to draw a line under past heavy-handed US intervention in the island's affairs, Obama vowed that "Cuba's destiny will not be decided by the United States or any other nation."
The US leader also said, without making any promises on timing, that "the embargo is going to end." He insisted that Washington was not going to give up pressing for political freedoms in Cuba, where the Communist Party controls politics, the media and the economy. The United States "will continue to speak up on behalf of democracy," Obama said. But the US president also appeared determined to move beyond the obstacles that have long made relations with Cuba a diplomatic dead end.
"Fortunately, we don't have to swim with sharks to achieve the goals you and I have set forth," he joked, referring to Nyad's feat. In only his third formal meeting with Castro, Obama was greeted by a military band that played the Cuban and the US national anthems. Under pressure back home to show that his scrapping of deeply rooted US hostility to the Castro regime will pay off, Obama then sat with the Cuban president against a backdrop of tall tropical plants.
Earlier he laid a wreath at the monument of Cuban independence hero Jose Marti. On Tuesday, he was to give an address carried live on Cuban state television, and then attend a baseball game between the national team and Major League Baseball's Tampa Bay Rays, before flying out. Obama's visit has raised hopes among struggling Cubans that decades of economic and political stasis may be coming to an end. But the brief detention of dozens of pro-democracy protesters hours before Obama's arrival Sunday served as a stark reminder of the regime's iron grip on power.
And despite the excitement among ordinary Cubans, officials appeared to be taking pains to give a restrained welcome. Castro did not greet Obama at the airport Sunday, sending his foreign minister instead, and a heavy police presence has ensured that Cubans have no chance of gathering spontaneously at any of Obama's appearances around the city. "I think Raul does not want a warm relationship with the US. He sees it in limited terms for the moment - tourism revenue and remittances plus the changes to the sanctions," said Paul Webster Hare, a former British ambassador to Cuba who teaches international relations at Boston University. Obama's administration is betting that forcing Cuba to open up diplomatically, as well as a gradual relaxation of the embargo, will promote democratic change. But Obama is defending himself from critics who say he has given away too much.