Investigations of the energy spectrum as well as the mass composition of cosmic rays in the energy range of PeV to EeV are important for understanding both, the origin of the galactic and the extragalactic cosmic rays. The multi-detector arrangement of KASCADE and its extension KASCADE-Grande was designed for observations of cosmic ray air showers in this energy range. Most important result from KASCADE is the proof that the knee feature at several PeV is due to a decrease in the flux of light atomic nuclei of primary cosmic rays. Results of KASCADE-Grande have now shown two more spectral features: a knee-like structure in the spectrum of heavy primaries at around 90 PeV and a hardening of the spectrum of light primaries at energies just above 100 PeV. These features are meanwhile confirmed by other experiments like Tunka, IceCube/IceTop, or TA/TALE. In this seminar the recent results on energy spectrum and composition are compared to each other and with astrophysical models for the energy range, where the transition from galactic to extragalactic origin of cosmic rays are expected. In addition, the effects of using different hadronic interaction models for interpreting the measured air-shower data will be discussed. Finally, the KASCADE Cosmic Ray Data Centre (KCDC) is discussed, which is a web-based platform to provide astroparticle physics data for the general public. The main purpose of KCDC is to archive original data to offer long-term scientific data for the high-energy astroparticle physics community as well as for students and the interested public via a sophisticated web portal. However, KCDC can only be a first step into a global analysis and data centre for multi-messenger astroparticle physics.