Pope Benedict meets Cuba's revolutionary icon Fidel Castro in Havana.

For about half an hour in the Vatican embassy... the pontiff and 85-year-old Castro discuss world events, science and the Church.

This after Benedict delivers an open-air mass before an estimated 300,000 in Revolution Square....

Crowds wildly welcome Benedict as he arrives in his popemobile.

Surrounded by ten-story high images depicting heroes of the revolution, Benedict urges Cuba to keep expanding religious freedom.

(SOUNDBITE) (Spanish) POPE BENEDICT SAYING:

"It must be said with joy that in Cuba steps have been taken to enable the Church to carry out her essential mission of expressing her faith openly and publicly. Nonetheless, this must continue forward, and I wish to encourage the country's government authorities to strengthen what has already been achieved and advance along this path of genuine service to the true good of Cuban society as a whole."

Cuba's President Raul Castro, Fidel's younger brother, hears the mass from the front row and is then invited to greet the pope.

Throughout his three-day visit to the island nation, Benedict has spoken of Cuba's need for reconciliation and a more open society.

Katharine Jackson, Reuters.