Soviet Army soldiers sit on their tanks in front of the Czechoslovak Radio station building in central Prague during the first day of Soviet-led invasion to then Czechoslovakia on August 21, 1968. (Photo by Libor Hajsky/Reuters)

Canada's Mandy Marchak (R) is taken down by France's Pauline Biscarat during the final match of the Hong Kong Sevens rugby women's invitational cup in Hong Kong March 28, 2014. (Photo by Tyrone Siu/Reuters)

“Himalayan Dog”. This dog just appeared out of nowhere and followed us for an entire week during our trekking trip in the Himalayan outback. He always used to sleep in front of our tent and guarded us in the nights. When I decided to get up at 4 a.m. to climb the next 5000 m peak for sunrise he accompanied me as well. On the top he was sitting for the entire 30 minutes on this place looking straight into the countryside. Photo location: Ladakh, India. (Photo and caption by Sebastian Wahlhuetter/National Geographic Photo Contest)

The “Escape Velocity” moving sculpture by artist group Poetic Kinetics looms over Coachella festivalgoers on the Empire Polo Field, on the first day of the 2014 Coachella Music and Arts Festival in Indio, California, on April 11, 2014. (Photo by Chris Pizzello/Invision)

Inês Carvalho (C), accompanied by her sister and cousin, is helped by her aunt to dress up at Alfama neighborhood in Lisbon on June 12, 2014. Carvalho, 18, is one of the revelers from the Alfama march and every Saint Anthony's day, Lisbon's protector, she parades with several other typical neighborhoods of the city. (Photo by Patricia De Melo Moreira/AFP Photo)

“Are you here for the Winery Tour?” This is a Western Grey Kangaroo caught lounging in the wineries of the Adelaide Hills in South Australia. This past Autumn has been a spectacular time for wildlife viewing and I got lucky to spot this guy while mountain biking in the hills. Such a funny stance it just begs the question... Have you been drinking? ...and or... Are you here for the Winery Tour? Such a spontaneous moment I figured it would be perfect for an entry. I hope you like it! Cheers. Photo location: Adelaide Hills, South Australia, Australia. (Photo and caption by Greg Snell/National Geographic Photo Contest)

“Theyyam”. Preparation for the Theyyam performance in the surroundings of Kasaragod city. Theyyam is a popular ritual dance form of North Kerala, particularly in Kannur and Kasargod districts. The Theyyam represents a mythological, divine or heroic character. Make up of Theyyams is done by specialist. There are different types of face painting for which primarily and secondary colours are used. Therefore it is essential that the makeup man should have perfect knowledge of primary and secondary colour combinations. Sometimes, it takes several hours to paint each face. Photo location: Kasaragod, India. (Photo and caption by Rafal Ziejewski/National Geographic Photo Contest)

Revelers throw a woman to the air during the opening and the firing of the “Chupinazo” rocket which starts the 2014 Festival of the San Fermin Running of the Bulls on July 6, 2014 in Pamplona, Spain. The annual Fiesta de San Fermin, made famous by the 1926 novel of US writer Ernest Hemmingway entitled “The Sun Also Rises”, involves the daily running of the bulls through the historic heart of Pamplona to the bull ring. (Photo by Pablo Blazquez Dominguez/Getty Images)