Airports of London Heathrow, more than Paris and Frankfurt combined, and Heathrow is the European terminus for 11 of the 25 busiest north Atlantic routes. The busiest long-haul route in the world is between London (Heathrow and Gatwick) and New York (JFK and Newark), with a total of 3,898,460 passengers travelling between the two cities in 2011. Airports of London The metropolitan area of London, England, United Kingdom is served by six international airports and several smaller airports. Together, they make the busiest airport system in the world by passenger numbers and the second-busiest by aircraft movements. In 2016, the six airports handled
Underground city boasts the city of Petra — "rose-red city, half as old as time" — carved from the living rock. Guanajuato city was built over old silver mines, some of which are used as roads. The Mexico DF metro system has many underground pedestrian walkways connecting stations. In general, many large railway stations house underground hallways featuring shops, restaurants, banks and money exchange offices. A striking example of such stations would be the main hallway of the Amsterdam central station, which connects to the city's metro system, although due to renovation and re-building it was temporarily (2012–2015) not possible to walk