US Treasury Secretary Janet Yellen visits the island of Goree, located off the coast of Senegal's Dakar and once the largest slave trading centre on the African coast, as she begins her African tour. "I can't help but think of the unspeakable cruelty of those who were engaged in the slave trade," says Yellen after touring the island with its mayor, Augustin Senghor. "What I take from this place is the importance of redoubling our commitment to fight for our shared values and principles," she adds. IMAGES AND SOUNDBITES