Image provided by Cubadebate shows Cuba's President Raul Castro (C, front) and US President Barack Obama (R, front) inspecting the guard of honour at the Palace of the Revolution, in Havana, capital of Cuba on March 21, 2016. Barack Obama on Monday paid tribute to Cuban national hero Jose Marti in Havana, starting the official program of his historic visit to Cuba to strengthen the approach between the two countries. [Photo/Xinhua]