The ancient remains of Rome's majestic Coliseum, once home to gladiatorial combats witnessed by audiences 50,000 strong.  Dedicated in A.D. 80, and rising four stories aboveground, this massive circular arena has 80 entrances and boasted an awning on the topmost level to protect spectators from the blazing Roman sun.  Gladiators, wild animals, staged naval battles, and executions claimed the lives of tens of thousands of animals and humans alike for at least three centuries.