Exceptional visits of the CMS CERN underground detector in Cessy (France), open to local primary and secondary schools.

A kid visiting the CMS detector

Every once in a while, the 27-km underground LHC tunnel, the world's largest scientific instrument, located below the Franco-Swiss countryside, is shut down and, as a consequence, exceptionally open for underground visits.

Enjoy a 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.

    1.30 - 2 hours
    Âge minimum
    Âge maximum
    Other language (subject to availability)
    Time of the year
    Every 2-3 years

    Site de CMS – LHC point 5
    D15G, 01170 Cessy, France

    Procédure d'inscription

    Free of charge, limited places. Next edition to be announced.

    Plus d'informations

    Please read the CMS safety instructions and the following conditions carefully:

    • Free of charge, limited places
    • Registration mandatory via an online form (no registration by email)
    • 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 12 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
    • /!\ To participate in the tour, you must provide the following sensitive 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. 

    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.