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)

The 150-square-metre Villa Ypsilon was designed by London- and Brussels-based firm LASSA, which is headed up by architects Theo Sarantoglou Lalis and Dora Sweijd.

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)

Labourers walk near trucks loaded with logs, which are trapped on a muddy road, near an unreserved forest in the village of Igbatoro, southwest Nigeria, August 28, 2014. Wood, a form of biomass, is the sole source of energy for hundreds of millions of Africans who lack access to modern sources of power, and logging, both legal and illegal, remains a lucrative business that has contributed to the rapid shrinking of Africa's rainforests and woodlands. (Photo by Akintunde Akinleye/Reuters)

The Angel Oak Tree is a Southern live oak located in Angel Oak Park on Johns Island near Charleston, South Carolina. The Angel Oak Tree is estimated to be at least 400 years old[citation needed]. It stands 66.5 ft (20 m) tall, measures 28 ft (8.5 m) in circumference, and produces shade that covers 17,200 square feet (1,600 m2). Its longest branch distance is 187 ft. in length. Angel Oak was the 210th tree to be registered with the Live Oak Society.

French photographer Laurent Chehere's “Flying Houses” exhibit takes workaday houses and lets them lift the imagination. The exhibit is showing at the Muriel Guépin Gallery in New York. Photo: Laurent Chehere's “Flying Houses”: “The Great Illusion”. (Photo by Laurent Chehere)

Gohei Hayashi of Kyoto University is seen in side his movable eco and healing house, “Kujira (Whale) House” July 21, 2007 in Tokyo, Japan. The house is made from Japanese paper, bamboo and tatami mat. Hayashi has travelled 500 km from Japan's ancient city, Kyoto to Tokyo with his eco house to promote his house which can be placed both out inside and outside to provide a private space. The Kujira house is available at the price of 800,000 yen (roughly US$6600). (Photo by Koichi Kamoshida/Getty Images)