The CERN Open Days have become a regular feature of the period called the “long shutdown” during which the accelerators stop for around two years, to benefit from upgrades and renovation work.
The last edition of the Open Days happened in September 2019. It gave 75'000 visitors the chance to discover CERN's facilities, both underground and on the surface. With free admission to debates, film screenings, theatre performances, experimental workshops and dozens of visit points spread all over the site, CERN volunteers take the visitors to the heart of the Laboratory during two days.
On many CERN sites
Website of the last edition: https://opendays.cern/