CMS Cavern

The Compact Muon Solenoid (CMS) is a general-purpose detector at the Large Hadron Collider (LHC). It has a broad physics programme ranging from studying the Standard Model (including the Higgs boson) to searching for extra dimensions and particles that could make up dark matter. Although it has the same scientific goals as the ATLAS experiment, it uses different technical solutions and a different magnet-system design.

The CMS detector is built around a huge solenoid magnet. This takes the form of a cylindrical coil of superconducting cable that generates a field of 4 tesla, about 100,000 times the magnetic field of the Earth. The field is confined by a steel “yoke” that forms the bulk of the detector’s 14,000-tonne weight.


After a short introduction on the CMS experiment, visitors are guided in the CMS assembly hall on the surface where a real size picture of the underground detector allows them to get a good idea of its size. Then group of visitors are taken 100 metres underground to see the service cavern of the experiment: counting room, monitoring equipments and an earlier control room. Visitors can also be taken through the current control room on the surface. Despite this is an underground tour, seeing the actual CMS detector is not part of it as the detector is inaccessible when the LHC is running (most of the year).
Standard opening times
Mon-Sat 08:00-19:00
Distance from CERN Reception (km)
Maximum capacity
Maximum number of visitors per guide
Minimum duration (min.)
Average duration (min.)
Minimum age
Accessible to pregnant women
Accessible to pacemaker, implants etc.
Accessible to reduced mobility
Accessibility details
Due to strong magnetic fields this visit is not accessible to wearer of pacemakers. The visit includes taking a lift 100 metres underground. Note that this underground visit DOES NOT include seeing the actual detector.
Underground site
Requires IMPACT

Description is given for information only and, as a result, imply no commitment from CERN Visits Service that they will be included in a visit programme. Any visit programme, even confirmed, is subject to last-minute changes due to operational or safety reasons.

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