The world’s most powerful particle accelerator will shutter operations Monday for four years of renovations to dramatically boost its collision capacity and the potential for unlocking one of the greatest mysteries of the universe: dark matter.

The Large Hadron Collider (LHC)—a 27-kilometer (17-mile) proton-smashing circular tunnel at the heart of Europe’s physics lab CERN near Geneva—has most famously been used to prove the existence of the Higgs boson, dubbed “the God particle.”

In the tunnel, running about 100 meters (330 feet) below the French-Swiss border area, superconducting magnets and accelerating structures propel particles to extreme energies and then smash them together at phenomenal speeds.