While a great deal of Pacific Rim's visual effects are done with CGI, there are many practical effects as well, as director Guillermo del Toro shows us in the latest featurette. The filmmaker takes us inside the massive sets that were built for the Jaeger heads, which stood four stories tall and simulated these robots motions in real time. Stars Charlie Hunnam and Idris Elba discuss the experience of working on this massive stage in this behind-the-scenes video for the highly-anticipated summer action-thriller, in theaters July 12.