Air travelers in Denver are treated to a solar-powered, covered parking lot, mini-golf, a nearby wildlife refuge and two on-campus commuter rail lines. In Dallas-Fort Worth, local authorities recently approved plans for a six-story, extended-stay hotel on an existing 32-acre, mixed-use commercial space that already has offices, restaurants and retail shops. In Pittsburgh, private businesses have invested several hundred million dollars for manufacturing, industrial, office and warehouse space on airport property – and aggressive efforts to bring more direct flights to Pittsburgh International Airport are attracting new types of business to this former steel town.

Passenger Chris Karnes describes the moment an Amtrak train derailed and crashed onto a highway below in Washington state.

Urban visited the big cities of Tokyo, Osaka, and Hiroshima, as well as Kyoto and lots of tucked-away hamlets. Once the train doors close at the beginning of the video, you plunge instantly into this temporal schism, from wondrous techno delights to scenes steeped in history.

A tube worker being lowered into a tunnelling shaft in Cavendish Square during work on London Underground's new Victoria Line. According to author Will Hunt, there are whole worlds. In his first book, Underground: A Human History of the Worlds Under Our Feet, Hunt takes readers on a journey through the catacombs, Cold War bunkers, subway systems and ancient burrows around the world. For over a decade, he traveled, along with urban explorers and scientists, through subterranean landscapes so few humans dare to tread, in order to discover new insights into human nature. It turns out that the damp, dark spaces miles below our daily life have a lot to tell us about how we think and live.