An Oct. 28, 1985 photo of John A. Walker Jr., being escorted by a federal marshal as he leaves the Montgomery County Detention Center in Rockville, Md., enroute to a federal court in Baltimore. He was ultimately sentenced to life in prison on espionage charges. Bob Daugherty/AP hide caption

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President of Ukraine Petro Poroshenko (left) and EU Commission President Jose Manuel Barroso during a news conference after a meeting at the EU Commission headquarters in Brussels on Saturday to discuss the crisis in eastern Ukraine. Julien Warnand/EPA/Landov hide caption

itoggle caption Julien Warnand/EPA/Landov

Hadrian's Wall marks the Roman Empire's northernmost boundary, and at one point is less than a mile from today's border between England and Scotland. Ari Shapiro/NPR hide caption

itoggle caption Ari Shapiro/NPR

Britain's Prime Minister David Cameron speaks at a news conference in London on Friday after the U.K. raised its terror alert level. Paul Hackett/PA Photos/Landov hide caption

itoggle caption Paul Hackett/PA Photos/Landov