From Geneva international airport at Cointrin
Taxi - approximately 35CHF.
Bus - First take a free public transport ticket from the machine you will find at the exit to the baggage collection hall, just before customs control. Then -
Option 1: Take bus Y direction "Val-Thoiry" and get off at the CERN stop opposite the large Globe and the CERN site.
See the TPG website for full details.
From Geneva railway station at Cornavin
Tram - Take the number 18 tram to "CERN" which is the final stop at the CERN entrance.
Ticket costs 3.00CHF (choose "Tout Genève" on the ticket machine). See the TPG website for full details.
Follow signs for "Aéroport", "Lyon" and "Meyrin". Once you are in Meyrin, follow signs for "St Genis" (which is just beyond the border, in France). Before reaching St Genis, the CERN site is on your left on "Route de Meyrin", just before you reach the border.
From France (département of Ain):
Follow signs for "Gex" or "St. Genis". When you reach the border, CERN is on your right immediately after passing through customs.
Once you get here...