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)
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)
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.
Participants wearing historical costumes ride their high-wheel bicycles during the annual penny farthing race in Prague, Czech Republic November 5, 2016. (Photo by David W. Cerny/Reuters)
Richard Kilty of Britain celebrates after winning the men's 60 metres final during the European Indoor Championships in Prague March 8, 2015. REUTERS/David W Cerny (CZECH REPUBLIC - Tags: SPORT ATHLETICS)
A baby hippo swims under the water in its enclosure at Prague Zoo, Czech Republic, February 24, 2016. The baby was born on January 28, and is yet to be named. (Photo by David W. Cerny/Reuters)
A child looks at a polar bear swimming under a water in its enclosure on a hot summer day at Prague Zoo, Czech Republic, July 30, 2015. (Photo by David W. Cerny/Reuters)