The Iraqis are building a wall around Baghdad to stop Jihad barbarians from driving into the city and blowing it and its people up.
If anyone thinks this is reminiscent of the later Roman Empire and the Dark Ages, they’d be right. The wall will be three meters high, made of concrete and backed up by a trench, or “moat.”
Constantinople’s walls were considerably larger and held back the barbarians until the 15th century. We’ll see how long Baghdad’s new wall lasts and have to ask how many other cities will follow suit. 
Some Americans believe that a wall should be built around Detroit, but that would be to keep the barbarians in.