It's a 27km ring of superconducting magnets with a number of accelerating structures to boost the energy of the particles along the way.
Inside it, two high-energy particle beams travel at close to the speed of light before they are made to collide.
The beams travel in opposite directions in separate beam pipes, which are two tubes kept at ultra-high vacuum.
They're guided around the accelerator ring by a strong magnetic field maintained by superconducting electromagnets.
The electromagnets are built from coils of special electric cable that operates in a superconducting state, efficiently conducting electricity without resistance or loss of energy.
"Thousands of magnets of different varieties and sizes are used to direct the beams around the accelerator," Cern says.
These include 1232 dipole magnets 15m long, which bend the beams, and 392 quadruple magnets, each 5m to 7m long, which focus the beams.
Just before collision, another type of magnet is used to "squeeze" the particles closer together to increase the chances of collisions.
The particles are so tiny that the task of making them collide is akin to firing two needles 10km apart with such precision that they meet halfway.
It's used to test the predictions of different theories of particle physics, high-energy physics and in particular, to further test the properties of the Higgs boson, as well as to answer many other unsolved questions of physics and to ultimately boost our human understanding of physical laws.
It is so sensitive, Auckland University physicist Richard Easther explained, that it would pick up any large quake when running.
"Despite being 27km in circumference, the Large Hadron Collider is enormously sensitive to small changes in its environment," Easther said.
"Particles move in both directions round the underground circle at up to 99.999999 per cent of the speed of light and the scientists operating the accelerator are always adjusting the "beam" to make sure that the particles stay on course.
"Even though Switzerland is on the other side of the world from New Zealand, the shaking from our big earthquake clear threw the particles inside the LHC off-track, even though the tremor would have been completely imperceptible to a human being."
