Pittsburgh, once referred to as "the smoky city" and "hell with the lid off" because of its sooty factories, is a modern success story. Air quality controls, stream purification laws, and the razing and redesign of congested areas since World War II have resulted in a city that surprises first-time visitors. Nestled among the forested hills of southwestern Pennsylvania at the point where the Allegheny and Monongahela Rivers form the Ohio River, the new Pittsburgh is a city of skyscrapers, parks, fountains, more than 700 bridges, and close-knit neighborhoods with a vibrant cultural life. The city has over 70 miles of urban riverfront—more than any other inland port city in America. The transformation of Pittsburgh from an industrial center to a leader in science and technology and the success of its rehabilitation efforts have moved President George W. Bush to call it "Knowledge Town," and the Wall Street Journal to rank it as one of the top technology markets (going so far as to nickname it "Roboburgh").