Dr. P.A. Smithe was sent by the American Red Cross as a doctor and surgeon to work at a hospital in Vienna. He sailed to Europe in December 1915 and returned home in August 1916, according to his daughter, who donated his images to the National World War I Museum. Photo: Turkish army, including cavalry, infantry and artillery. (Photo by Dr. P.A. Smithe/National World War I Museum, Kansas City, Mo.)

A detail of the Sagrada Familia Basilica, designed by architect Antoni Gaudi, in Barcelona, Spain, Wednesday, October 21, 2015. Barcelona's breathtaking La Sagrada Familia Basilica has begun its final phase of raising six immense towers. Presenting the project Thursday, chief architect Jordi Fauli said the central "Tower of Jesus Christ," the tallest of the six, will rise 172.5 meters (566 feet) high, making it "the tallest religious building in Europe". (Photo by Manu Fernandez/AP Photo)

Thousands of species of amphibians are endangered and hundreds have already disappeared, but in recent years, a team of scientists and conservationists have re-discovered some of these “lost” species and uncovered previously unknown varieties. Here: Miniature glass frog. (Photo by Robin Moore)

People dressed as zombies take part in a “Zombie Walk” parade in Athens, Greece, February 25, 2017. (Photo by Michalis Karagiannis/Reuters)

Jaheel Hyde, of Jamaica, competes in a men's 400-meter hurdles heat at the 2024 Summer Olympics, Monday, August 5, 2024, in Saint-Denis, France. (Photo by David J. Phillip/AP Photo)

Actress Maddie Ziegler holds her bag as she poses during People's “Ones To Watch” event celebrating Hollywood's rising and brightest stars in West Hollywood, California September 16, 2015. (Photo by Kevork Djansezian/Reuters)

A curious leopard cub toys with a camera at MalaMala Game Reserve in Mpumalanga Province, South Africa. (Photo by Barcroft Media)

Actress Edy Williams attends the 58th Annual Academy Awards on March 24, 1986 at Dorothy Chandler Pavilion in Los Angeles, California. (Photo by Ron Galella/WireImage)