CERN: the next 60 years and 100 kilometers

CERN is undertaking the design study of Future Circular Colliders fitting in a new tunnel of 100km circumference around Geneva. A possible first step is the "Electroweak Factory", a high luminosity electron-positron (lepton) collider covering the energy range from the Z pole to above the top threshold, for the study of several TeraZ, okuW, MegaHiggs and Megatops. The tunnel would fit, as ultimate goal, a 100 TeV pp collider. The project will be described with special attention to the electron machine.
The combination of the two machines offers a remarkable potential for discoveries, from a blend of precision measurements, high statistics, high energies and sensitivity to very small couplings. In particular the search for sterile right-handed neutrinos (aka neutral heavy leptons), with mass up to the Z mass, will be shown to reach couplings as small as predicted by the see-saw limit.