Nothing remains of the mysterious roof covering Ancient Rome’s most infamous of amphitheatres. It protected 45.000 spectators from the fierce midday sun, as they watched wild animals and humans fight and die. How did the Ancient Romans build such a giant susended structure, when engineers can barely do it now? World expert Rainer Graefe believes that he has the solution. Top engineer Chris Wise disagrees. Both set out to prove the other wrong, and build a Colosseum roof for the first time in 2.000 years.