Veritasium created a nice experiment to prove the fact that you can create a void inside a drum. Just insert some water inside the drum, heat it up, then put some corks to cover the holes and then throw cold water at the drum. Inside the drum the water vapors will condense and it will create a void.
Normally it would collapse in itself, but some round objects are too strong and they can overcome that. Veritasium created a ripple in the drum and that generated a surplus of tension in that point . In return the drum collapsed into a prism since the prism is the shape that covers the smallest amount of volume when it comes to cylindrical objects.
Incredible experiment and incredible feats. Enjoy.