During its long shut-down, the 27-km underground LHC tunnel, the world's largest scientific instrument, located below the Franco-Swiss countryside, is exceptionally open for underground visits.

Enjoy the unique opportunity to visit the CMS (Compact Muon Solenoid) particle detector 100m under the town of Cessy (FR)! This detector is the only LHC site accessible to visitors under 16 years old.

Take a walk in the cathedral-sized cavern that houses the twenty-two meter-long, 15 meter-high, and 14’000 tons (twice the Eiffel Tower) detector.


Please read the CMS safety instructions and the following conditions carefully before registering your class.

  • Free of charge, limited places
  • Registration mandatory via the online form before Saturday 29 February.
  • Organization and transportation fees to be covered by the schools
  • Open to classes from local primary and secondary schools (located within 30 km of CERN)
  • Group of minimum 20 participants, maximum 36 or 48 depending on the time slot
  • Minimum age: 8 years old (no exception possible)
  • Minimum of 1 accompanying adult for 5 pupils aged 8-16; or for 11 pupils aged 16-19
  • Total duration of the visit: between 1h30 and 2h according to the number of participants
  • Date and time of the visit must be chosen during registration, between 12 March and 30 June 2020.
  • /!\ To participate in the tour, you must provide the following data about ALL participants (children and adults): name, first name, date of birth, place of birth and nationality. We will need to receive this information at last 2 weeks before the visit. We will send you more instructions once your visit has been validated. 


Please note that:

  • There is no lunch facility on the CMS site and picnics are prohibited on the site
  • Provided helmets must be worn while underground
  • Closed flat or block heeled shoes must be worn during the visit.
  • For reasons beyond our control, the detector may not be accessible on last notice. If that happened, we would try to find a solution.


From 12 March to 30 June 2020 (several slots on Tuesdays and Thursdays)


Between 1h30 and 2h according to the number of participants

Minimum age


Maximum Age



English, French (other languages can be considered)


Site de CMS – LHC point 5
D15G, 01170 Cessy, France
GPS: 46.310819 N, 6.078311 E

How to sign up

Fre of charge, limited places
Mandatory registration on from 10 to 29 February 2020


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