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)

Twenty five life-size donkeys have been given pride of place in St Paul's Cathedral as part of an interfaith exhibition. They've been painted by Egyptian and Western artists, to show solidarity for the people of Egypt. Photo: Artist painted donkey statues are displayed in the “Caravan” exhibition on August 30, 2013 in London, England. (Photo by Peter Macdiarmid)

Competitors take part in the International Medieval Combat Federation World Championships at Scone Palace on May 10, 2018 in Perth, Scotland. Thousands of visitors are expected to attend the crowning place of Scottish Kings, Scone Palace for the IMCF World Championships which has five hundred competitors and officials from all over the world, from the UK to as far afield as Australia, South Africa and Mexico. (Photo by Jeff J. Mitchell/Getty Images)

A girl attends Friday prayers in front of an army tank in Tahrir Square in Cairo February 18, 2011. Five years ago thousands of protesters took to the streets demanding the end of the 30-year reign of President Mubarak as Egypt became the second country to join the Arab Spring. After weeks of clashes, strikes and protests across Egypt, Mubarak resigned on February 11, 2011. (Photo by Suhaib Salem/Reuters)

A member of staff stands in front of a CRH high-speed train at Shanghai Hongqiao Railway Station during its test run on May 11, 2011 in Shanghai, China. After 3 years construction, from April in 2008, with total investment estimated at 220.9 billion yuan (around 32.5 billion U.S. dollars), the Beijing-Shanghai high-speed railway begins a one-month trial operation. It is expected to start operation in June this year, with the travel time between the two cities reducing to five hours from the previous 10. (Photo by ChinaFotoPress/Getty Images)

A five-month-old female slender loris waits to be given her first health check by the veterinary team at London Zoo on July 21, 2011 in London, England. Two female baby slender lorises, who are yet to be named, were given health checks, their s*x determined and micro-chipped. Slender Loris is the common name for the strepsirrhine primates who are nocturnal and originate from India, Sri Lanka, and southeast Asia. London Zoo supports conservation of lorises in Sri Lanka, where populations are thought to be under threat from deforestation. (Photo by Christopher Furlong/Getty Images)

More than 700 underwater images were submitted for the 2012 Annual Underwater Photography Contest, hosted by the University of Miami's Rosenstiel School of Marine & Atmospheric Science. This year, for the first time, the University of Miami set up a “Fan Favorite” category for its underwater photo competition. Internet users could vote for their favorite among five pictures. Todd Aki's photo of a jellyfish took the prize, snaring 599 of the 1,221 votes cast. (Photo by Todd Aki)