Inside the cavern

After 2 excellent lectures on particle detector technology, in the afternoon we had the opportunity to visit the service cavern of CMS (compact muon solenoid). At the moment particles are accelerated in the LHC (large hadron collider), so we cannot get to the detectors (radiation risks). But this visit was as close as we could get to the LHC.
PS: This cavern is 90m underground...