HAVANA, Cuba — President Barack Obama arrived in Havana on Sunday on a historic visit rich in symbolism and defined by high expectations for a new era of U.S.-Cuban relations after decades of Cold War hostilities between the two countries.

Air Force One touched down at Havana’s Jose Marti International Airport after 4 p.m. Eastern Time. The president and his family plan to spend two-and-a-half days in Havana, leaving Tuesday afternoon for a stop in Argentina.

Obama held an umbrella as he descended the steps from Air Force One with Mrs. Obama into the rainy Cuban afternoon. He was greeted by Cuba’s foreign minister and other top Cuban diplomats, along with the ranking U.S. diplomat in Havana. As the presidential plane was landing, Mr. Obama sent a Twitter message intended for Cuban people: “Que bolá?” meaning “What’s happening?”

Obama’s trip to Cuba — the first for a sitting American president since Calvin Coolidge in 1928 — comes 15 months after he and Cuban President Raúl Castro announced an agreement to restore diplomatic relations.

Obama’s first remarks of the trip came in an informal meeting with U.S. embassy staffers at a local hotel, erroneously referring to the highest ranking U.S. diplomat in Havana, Jeffrey DeLaurentis, the U.S. charge d’affairs, as “ambassador.” The U.S. doesn’t yet have an ambassador to Cuba.

“Today is a historic visit and a historic opportunity,” he told the U.S. staffers and their families.

President Obama Arrives in Cuba for Historic Visit

In an ominous sign hours before Obama’s arrival, Cuban security agents detained dozens of members of the dissident group Ladies in White, who were holding their weekly protest in Havana to demand the release of political prisoners.

Later Sunday, Obama was to take a walking tour of Old Havana. During the tour Obama plans to visit the city’s Roman Catholic cathedral. He’ll be greeted there by Cardinal Jaime Ortega, who, along with Pope Francis, helped facilitate the detente between the U.S. and Cuba that led to Obama’s historic state visit.

An expanded version of this report appears on WSJ.com.