This question already has an answer here:
- Visiting CERN in Switzerland 3 answers
Any ideas as to how one might go about getting a tour of the Large Hadron Collider?
As it turns out it is possible during the Open Days, which unfortunately in 2013 had taken place on September 28th and 29th. And as of right now there are no such Open Days published for the year 2014.
For details you can probably start with the Practical Information page regarding visiting, which is not likely to change much from 2013 to 2014, whenever those dates become available.
The Hadron Collider is part of the CERN (European nuclear research center).
From a quick googling…
There seems to be some "open days" where there are organized visits.
Have a look at: http://opendays2013.web.cern.ch/
Other than that, I think you will need at least some contacts and references from professors from universities associated with the CERN.
Maybe if you are a journalist (a real one) you might have access to the Collider, but you will still need references.
Or simply contact them.
If you take a broad definition of tour, to include virtual tour, you could consider Google Streetview, as the Large Hadron Collider was mapped
I visited the LHC on this years' open days. It was an experience I was glad I took part in. Some people even flew in for the day just to visit CERN. Such open days are unfortunately rather rare. Underground visits are only permitted when the LHC is on hiatus. When the collider is in operation you can't go down there, because of radiation risks, but more importantly because of the liquid helium used to cool the thing down, which is very dangerous.
Currently the LHC is down, and is being maintained (Which meant that we could even see some partly disassembled parts). Because of this more visits are planned. I know you can get a visit if you know the right persons. That's how I got a tour of the LHC when it was still under construction two decades ago. But I also know that it is possible that over the next year some more underground tours will be organised. Keep coming back to the CERN website for more information.