The HIE-ISOLDE project aims at several important upgrades of the present ISOLDE radioactive beam facility at CERN. The main focus lies in increasing the energy of the radionuclide beams from 3 MeV/u up to 10 MeV/u through the construction of a superconducting post-accelerator. The upgrade substantially enhances research opportunities in most aspects of nuclear structure and nuclear astrophysics, making ISOLDE the only facility in the world capable of accelerating medium to heavy radioactive isotopes in this energy range.