Me and my wife visited on our honeymoon, and we were expecting a more tourist-based tour with some basic info on what they did there. But we ended up with a group of A-Level Physics students, so we got a full-on in-depth Physics lesson! It was heavy going at times, but the guides/physicists are very enthusiastic about what they do and encourage you to join in and ask questions constantly.

We were also treated to a trip underground in the afternoon, visiting the CMS detector on the France side of the LHC. CERN put on a large coach to take you there, and again one of the physicists guides you around the place.

The big bonus of the whole thing is that it's entirely free. The basic tour, the coaches/buses, the extended tour, everything. And the physicists give up a few hours of their working week to come and show the visitors around as well.