Airports of London cannot be expanded due to the docks on either side. It is also the only airport serving London which does not operate at night. A light rail service from London City Airport DLR station, which adjoins the terminal building of London City Airport, links it to the financial district of the City of London at Bank and Monument stations, which offer interchanges with London Underground. Located in the London Borough of Hillingdon, Heathrow is by far the largest of London's airports and considered the main gateway into the United Kingdom for non-European visitors. Heathrow has four terminals and two parallel
Özkonak Underground City was probably built by the people of Byzantine Cappadocia, although the age is uncertain and could be older. The Özkonak Underground City was discovered in 1972 by a local farmer named Latif Acar, who was curious about where his excess crop water was disappearing to. Latif discovered an underground room which, when later excavated, revealed a whole city which could house 60,000 people for up to three months. Although only four floors are now open, the complex contains a total of ten floors, to a depth of 40m. Unlike the other underground cities in this area, there were holes above