Paramedics carry an injured woman out from a subway station after a rush-hour subway train derailment, to be transported by a medical helicopter in Moscow, Russia, on Tuesday, July 15, 2014. A rush-hour subway train derailed in Moscow Tuesday, killing 20 people and injuring at least 150, emergency officials said. Several cars left the track in the tunnel after a power surge triggered an alarm, which caused the train to stop abruptly. (Photo by Ivan Sekretarev/AP Photo)

Undated handout photo issued by World Architecture Festival 2013 of The Halley VI centre designed by British architects Hugh Broughton in Antarctica which is a dismantlable research station created in the icy wastes for the British Antarctic Survey and has been shortlisted for a global architecture award. (Photo by World Architecture Festival 2013/PA Wire)

A woman looks at La Paz city from the Jacha Qhatu cable car station in El Alto, July 23, 2015. Bolivia already has the largest urban cable car system in the world. Now the booming country is tripling the size of the network and will soon have nine lines whizzing above the administrative capital of La Paz. (Photo by David Mercado/Reuters)

Tube passengers take a selfie next to a London underground roundel designed for the launching of the Night Tubes on display at Oxford Circus underground station in London, Britain, 19 August 2016. The long delayed Night Tubes service launched on 19 August. The 24-hour service will operate on Fridays and Saturdays. (Photo by Hannah Mckay/EPA)

An actor performs during the show “Paris de Nuit” in Santiago, Chile, 20 September 2016. The show is a combination of cabaret and circus, produced by the Recirquel Contemporary Circus Company from Budapest, and will be performed at the Mapocho Cultural station from 20 to 25 September. (Photo by Mario Ruiz/EPA)

In 2013, the United Nations General Assembly officially designated November 19 as World Toilet Day, which is coordinated by UN-Water in collaboration with governments and partners. Here: An open-air toilet and a hot spring shower are seen in the middle of nowhere on the road to the Krafla geothermal power station and lava fields, near Reykjahlid and Lake Myvatn in northeastern Iceland, on August 19, 2012. (Photo by Mariana Suarez/AFP Photo)

Passengers wait at the departure hall of the Beijing Railway Station in central Beijing, China January 27, 2017 as China gears up for Lunar New Year, when hundreds of millions of people head home. (Photo by Damir Sagolj/Reuters)

One of the last incoming trains arrives outside the main train station after Deutsche Bahn cancelled all train traffic in Germany due to heavy storms, Frankfurt, Germany, Thursday, January 18, 2018. (Photo by Michael Probst/AP Photo)