The world millions of years ago: The dinosaurs were extinct, now new, fascinating giants are populating the earth. A twelve-meter-long giant boa and the ancient rhinoceros, which weighs several tons. Scientists from all over the world are compiling the latest findings about the prehistoric giants. Using modern CGI technology, they bring the extinct colossi in the documentary to new life. Will they manage to solve the final puzzles surrounding the mysterious giants? Central question: Why did the giant animals become extinct? The anaconda and today's rhinoceros are the closest living relatives that provide scientists with information about the behavior of the prehistoric giants. Fossil remains, the examination of important excavation sites and the latest digital technology provide a fascinatingly comprehensive picture of the life and death of the prehistoric giants. (Text: ZDF)