GBCs are cool because they’re built separately by many different users, then brought to a convention with the expectation that they’ll work together. I love the dizzying variety of ball-moving gadgets! This one was built by 7 Danish, Belgian, and Dutch builders with a world-record 93 mechanisms linked together. The contraption was featured at Lego World 2011 in Copenhagen.
World’s Largest Lego Great Ball Contraption