The Great Wall of Arabia

No, you won't be able to see it from space, but Saudi Arabia, unnerved by the violence next door in Iraq, plans to spend up to $7 billion on a partly virtual fence along its 500-mile border with Iraq. The ultramodern barrier will combine fencing, electronic sensors and sand berms. Saudi and U.S. sources tell TIME the kingdom is seeking bids from contractors, including U.S. defense giant Raytheon. (A Raytheon spokesman says the Saudis asked the company not to comment.)

Saudi diplomats say the fence is intended to stop weapons and drug smuggling and illegal immigration. But they admit they fear that Iraq's sectarian fighting and jihadi militancy could spill south. "We're worried about the war in Iraq coming into Saudi Arabia and spreading into the whole region," says Nail al-Jubeir, a spokesman for the Saudi embassy in Washington. "Having some of these guys heading toward the Saudi border is something we want to make sure doesn't happen."

While good fences may make good neighbors, this one will not ensure Saudi Arabia's security. The kingdom has had at least five deadly terrorist attacks since 2003, and some of the perpetrators were homegrown.