Like its cousin, the Holocaust memorial in Jerusalem, Rwanda's stunning new genocide museum, perched on a quiet hillside overlooking Kigali, is at its most arresting when it honours the lost children. One installation invites us to consider David, a cute, shy boy, with big round black eyes: David's favourite sport was soccer; he enjoyed making people laugh; his dream was to be a doctor; he was tortured to death; his last words were: 'The UN will come to get us.' Next to David's biography is Ariane's, four, stabbed in the eyes and head; Fillette, also four, smashed against a wall;...