A woman takes part in a four-minute flash mob pillow fight at the Old Town Square in Prague, Czech Republic, December 22, 2016. (Photo by David W. Cerny/Reuters)

This picture taken on September 9, 2014 shows a waiteress handing over food to customers at a prison themed restaurant in Tianjin. As more themed restaurants are popular in China, a “prison style” restaurent in Tianjin is aimed at reminding people to observe the law and to be good citizens. (Photo by Wang Zhao/AFP Photo)

A participant runs through colored powder as she takes part in the Get Rainbowed run in Prague May 23, 2015. Get Rainbowed is a five-kilometre race with the aim of promoting a healthy lifestyle. (Photo by David W. Cerny/Reuters)

An enthusiast dressed as a zombie takes part in the annual Zombie Walk festival in Prague June 1, 2013. (Photo by David W. Cerny/Reuters)

The Clementinum (Klementinum in Czech) is a historic complex of buildings in Prague. Until recently the complex hosted the National, University and Technical libraries, the City Library also being located nearby on Mariánské Náměstí. The Technical library and the Municipal library have moved to the Prague National Technical Library at Technická 6 since 2009. It is currently in use as the National Library of the Czech Republic. In 2005, the Czech National Library received the UNESCO Jikji prize (Memory of the World).

A waitress displays a plate of animal penises and testis at the Guolizhuang pen*s Restaurant on September 7, 2007 in Beijing, China. The restaurant offers more than 30 types of animal-pen*s dishes which can cost from 500 yuan (76.99 USD) up to 90,000 yuan (13,857.67 USD). It is believed that eating an animal's pen*s can strengthen a man's sexual ability. (Photo by Feng Li/Getty Images)

Located in Kunshan, eastern China, the restaurant relies on over a dozen machines for tasks such as greeting customers, waiting on tables and cooking basic meals. The eatery becomes the third café in the world to rely on the use of robot employees, potentially giving a glimpse into how future businesses could operate. Photo: This photo taken on August 13, 2014, shows a robot carrying food to customers in a restaurant in Kunshan. It's more teatime than Terminator – a restaurant in China is electrifying customers by using more than a dozen robots to cook and deliver food. (Photo by Johannes Eisele/AFP Photo)

The Prague astronomical clock, or Prague orloj, is a medieval astronomical clock located in Prague, the capital of the Czech Republic. The clock was first installed in 1410, making it the third-oldest astronomical clock in the world and the oldest one still working.