Jurassic Park may have helped revolutionize modern CG animation in movie-making, but out of the 14 minutes of dinosaurs in the movie, only four were completely generated by computers. Practical effects played a huge role, and none so much as a monstrous 40-foot long, 9,000-pound tyrannosaurus rex that the team built out of good old steel and hydraulics.

Stan Winston Studios was the effects house behind the animatronic creatures for the film, and it’s released 12 minutes of archival footage of the T. rex build, featuring commentary from engineers who worked on the project. “I don’t think anything has ever been attempted before or since that is as ambitious,” says Richard Landon, the project’s mechanical department coordinator. Granted, it’s a menacing sight in the workshop, but if you want to see the creature in all its glory, we’d recommend heading to an IMAX theater this week for a showing of Jurassic Park 3D.