Hadrian’s, Berlin and other great walls throughout history

One could be forgiven for thinking an era ended two decades ago when the Berlin Wall crumbled. After all, what could better illustrate how obsolete the ancient, stolid stone and concrete barrier had become than the sight of thousands of gleeful East and West Germans pulling apart the monstrosity by hand, piece by piece? The fact is that barriers remain an influential presence across the globe, 11 millennia into their known history. Today's walls serve many of the same purposes their historical predecessors did—defending against outsiders, confining populations, and halting commerce worldwide. Here's a look at some of history's most famous fortifications and some of their most imposing modern-day heirs.