This island in the middle of the Mediterranean exports granite and uses granite for most of its buildings. It's famous for the Costa Esmerelda, bought in 1960 by Karim Aga Khan and a group of his friends to develop an exclusive community, 3,000 hectares, along a spectacular coastline of beaches and granite hillsides. It's a vacation spot for the rich and famous, done in an environmentally sensitive way with unassuming architecture using local, natural materials – granite and juniper. Karen visited Baia, a lovely beach town, and Porto Cervo, an upscale village with a fantastical marina. Then we walked the streets of Olbia.