In Britain, giant Olympic rings floated down the Thames River in London to mark 150 days until the start of the Summer Games. The five iconic rings, measuring 11 metres tall, were unveiled on a barge yesterday as a tug boat pulled them toward the historic Tower Bridge. The Olympic symbol travelled east to the Thames Barrier before returning to Tower Bridge. London Mayor Boris Johnson launched the spectacle as he announced free cultural and entertainment events that will be held in London this summer to welcome the millions of visitors arriving for the Olympics. The games run from July 27 to August 12.