Urban photographer Roman Robroek spent five years scouring the continent for the grandest examples of forgotten architectural beauty. Here: Watch your step on this Polish spiral staircase. (Photo by Roman Robroek/South West News Service)

In the mountains of central Vietnam, a colossal pair of hands lifts a golden thread of walkway high above the clifftops, as if the mountain itself has sprouted limbs. Here: A giant hand structure at the Gold Bridge is seen on Ba Na hill near Danang city, Vietnam on August 1, 2018. (Photo by Reuters/Kham)

Kha Tu Ngoc rests in her two- square- meter house in Ho Chi Minh City on May 2, 2018. The “micro- house” dwellings are dotted throughout Vietnam' s bustling southern hub, occupied by families clinging to postage stamp- sized plots a city developing at breakneck pace. Tucked away in winding alleys, nestled under new condo developments or sandwiched between street food stalls and shops, the tiny houses are easily missed by the unattentive passerby. (Photo by Thanh Nguyen/AFP Photo)

A colourful morning sunrise on Christmas Eve at Victoria Tower on Castle Hill, West Yorkshire, England on December 24, 2017. The history of human activity on the Castle Hill goes back over 4000 years. The site was developed as an iron age hill fort, surrounded by defensive ditches and ramparts. In the Middle Ages there was a castle on the hill, of which the well remains. The present tower was built to commemorate Queen Victoria's Diamond Jubilee of 1897. (Photo by Charlotte Graham/ZUMA Wire/Rex Features/Shutterstock)

The buildings of the banking district are seen through thousands of rain drops on a glass railing in central Frankfurt, Germany, Wednesday, January 11, 2017. (Photo by Michael Probst/AP Photo)

Inspired by traditional Indian travelling photography studios, Arthur Crestani photographed the inhabitants of Gurgaon, a city built almost entirely by private companies. Arthur Crestani’s “Bad City Dreams” contrasts the glossy ideal sold by developers with urban reality. Here: Luxury Living Bhiwadi: “Sky Club on 18th Floor”. (Photo by Arthur Crestani/The Guardian)

At the Krasnopresnenskaya station, the benches come from the Cathedral of Christ-Sauveur, which was built from 1839 to 1883 in memory of the victory of Russia against the army of Napoleon I. The cathedral was destroyed under Stalin in 1931, but the benches remained intact. Metro architects decided to install them in some stations. (Photo by Didier Bizet/The Washington Post)

A soldier walks on the bank of the river in central Pyongyang, North Korea on April 16, 2017. (Photo by Damir Sagolj/Reuters)