The president minced no words about Trump's suggestion to reverse U.S. policy and encourage more countries to develop nuclear weapons.
"Be aware of immediate surroundings and avoid crowded places," according to the U.S. State Department travel alert.
Obama will meet with President Castro, attend a baseball game and deliver an historic address from the Grand Theater of Havana.
Obama's Supreme Court justice nominee is unlikely to even get a hearing.
The president challenges Senate Republicans to "do their jobs" and consider the nominee, while GOP leaders dig in their heels.
Emergency crews have cleared the scene after staffers for Marco Rubio's presidential campaign evacuated.
Gov. John Kasich comes in a close second among D.C. Republicans.
Significant amount of water in the building, according to Capitol Police.