Each week viewers see the gritty reality of life in a New York City Police unit as the officers go about their work with a grim determination. Two partners, Detectives Andy Sipowicz and John Kelley (later replaced by Bobby Simone), are the central characters in this weekly police drama, and personify very different approaches to their difficult job. Sipowicz's brash gruffness (...。In the heart of the Jordanian desert, the ancient city of Petra is full of mysteries. How was this architectural prowess achieved more than 2,000 years ago? © National Geographic。