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)

A picture rotated 180 degrees shows visitors walking inside an “Upside-down House” attraction at the VVTs the All-Russia Exhibition Center in Moscow, on January 14, 2014. The attraction to experience a new perspective of a house standing upside down was opened first time in Russia, the show organisers said. (Photo by Alexander Nemenov/AFP Photo)

Measuring just five feet at its widest point, the ultra-thin home was unveiled in the Polish capital of Warsaw on Sunday, October 21, 2012. Photo: The Keret House is squeezed into the space between two apartment buildings in Warsaw. There's a four-inch gap between the apartment buildings to either side. A perforated steel facade was used to allow in more light. (Photo by Andrea Meichsner/The New York Times)

Muslim women light candles during the “EarthHour” in Jakarta, Indonesia, on March 23, 2013. Hundreds of people observed the global event that encourages people to turn off their lights for 60 minutes. (Photo by Dita Alangkara/Associated Press)

In this March 29, 2016 photo, a man shoulders a coffin with the remains of a loved one who was slain more than two decades ago by Shining Path rebels, as he walks to the cemetery for a group burial service, in Ccano, a village in the Huanta area of Ayachcuo department, Peru. Presidential candidate Keiko Fujimori's base of support is in places like Ccano, where promises to build roads, clinics and schools recall her agronomist father’s own legacy of delivering aid to the long-overlooked countryside. (Photo by Rodrigo Abd/AP Photo)

An isolated five-floor building stands in the middle of a new road on November 22, 2012 in Wenling, Zhejiang Province of China. Zhejiang Province of China. 67-year-old Luo Baogen and his 65-year-old wife from Xiazhangyang village still live in the half-demolished residential building, because they are dissatisfied with the relocation compensation. The road, which leads to the Wenling Railway Station, has not been put into use. (Photo by China Foto Press)

A visitor poses inside a three story upside-down family sized house at the Huashan Creative Park in Taipei, Taiwan April 7, 2016. Over 300 square meters of floor space of the upside-down house, filled with home furnishings, was created by a group of Taiwanese architects at a total cost of around US$600,000 and took 2 months to complete, according to the organisers. (Photo by Tyrone Siu/Reuters)