With rapidly urbanizing metro areas, some cities are not looking to build up, or spread out, anymore. Rather they have begun to grow into underground spaces.
Sep 27, 2014 Bloomberg News
Singapore has built skywards and taken back land from the sea to accommodate its booming population. But as the city-state runs out of options for future growth, it's looking underground to build infrastructure, offices, and even public spaces.
Sep 26, 2013 The New York Times
The immense drill that's burrowing a subway tunnel beneath New York City will remain underground after its work is through, a move to cut the expensive costs of removing it.
Jul 26, 2011 The New York Times
Sidewalks in Holland have for years utilized piped-in waste heat to melt snow. Now, they've added an additional sidewalk amenity: a hearth.
Apr 14, 2011 Metropolis
The city of Helsinki has developed a master plan for its burgeoning underground city.
Feb 24, 2011 The Huffington Post
Construction is nearing completion on the longest railway tunnel in the world.
Feb 21, 2011 National Geographic
A new video features urban explorer Steve Duncan as he adventures in the abandoned subway tunnels beneath New York City.
Jan 6, 2011 Wired
Officials in Finland are building a nuclear waster storage facility that is designed to last for at least 100,000 years.
Nov 13, 2010 CNN
A six month trial will bring Wi-Fi Internet access into test locations within the London tube system, part of an effort by the city to bring Internet access to the entire system in time for the 2012 Summer Olympics.
Nov 4, 2010 BBC
103 artists form around the world have unveiled a massive collection of murals in New York City. But they're underground in abandoned subways stations, and you can't go see them.
Nov 4, 2010 The New York Times