NATO has reported a spike in Russian military activity at sea and in NATO and other western European countries' airspace as tensions have mounted over Ukraine. Here, a Russian military long-range bomber aircraft flies in international airspace on Oct. 29. Royal Air Force/AP hide caption

itoggle caption Royal Air Force/AP

Pedestrians pass the display windows at Bonhams New York auction house. The Mexican government accuses Bonhams of auctioning off artifacts that were stolen from Mexico, and says others that were offered as ancient were modern fakes. Bebeto Matthews/AP hide caption

itoggle caption Bebeto Matthews/AP

What do you get when three Israelis, two Iranians and a German walk into a room? A Berlin-based world music ensemble known as Sistanagila, named after an Iranian province — Sistan and Baluchestan — and the popular Jewish folk song "Hava Nagila." Courtesy of Sistanagila hide caption

itoggle caption Courtesy of Sistanagila

Chinese President Xi Jinping and President Obama, seen here during a ceremony at the Great Hall of the People in Beijing, announced pledges to reduce greenhouse gases. HUANG JINGWEN/Xinhua /Landov hide caption

itoggle caption HUANG JINGWEN/Xinhua /Landov