I am certainly no expert about CERN. But apparently there have been a series of colliders built, with the first one in 1959. Here is a drawing from wikipedia, that shows the dates associated with each collider. The biggest one, the LHC, Large Hadron Collider, collider, is 27 km long in a circular path, built in 2010.
Basically what the collider does is use giant magnets positioned around a tube, which accelerates sub atomic particles at a high rate of speed making a beam within the tube, which other particles are then interjected into the path of the beam going round-h-round, resulting in a collision that has some result(s) the scientists can then interpret.
Here is another link.
commons.wikimedia.org