An Iranian security guard directs media at the Bushehr nuclear power plant in 2010. The crisis in Ukraine, the Ebola outbreak in Africa and extremist violence in Iraq all threaten to complicate the nuclear talks. Vahid Salemi/AP hide caption

itoggle caption Vahid Salemi/AP

Displaced Iraqis from the Yazidi community settle under a bridge in central Dahuk, Aug. 14. Human rights activists say evidence of the Islamic State's violence against the Yazidis points to war crimes, and amounts to ethnic cleansing. Khalid Mohammed/AP hide caption

itoggle caption Khalid Mohammed/AP

An Iraqi child walks next an empty house of a Christian family in Mosul on Aug. 8. The Arabic writing on the wall reads "Real Estate of the Islamic State." The extremist group took control of Mosul, Iraq's second largest city, in June. STR/EPA/Landov hide caption

itoggle caption STR/EPA/Landov

Friar Gabriel Tooma leads a service at the Chaldean Church of the Virgin Mary of the Harvest, in Al-Qosh on June 15. At the time, the Christian village in northern Iraq was taking in those fleeing violence in the nearby city of Mosul. Now the village itself is largely deserted. AP hide caption

itoggle caption AP

The Hagia Sophia is one of the city's most well-known Byzantine monuments, but it's also home to a lesser-known memorial: a plaque for the man who encouraged the Fourth Crusade's plundering of the city. Bulent Kilic/AFP/Getty Images hide caption

itoggle caption Bulent Kilic/AFP/Getty Images