Interferometric gravitational wave detectors are amongst the most sensitive instruments ever built. They are hunting for tiny oscillations in space-time originating from cosmic events such as inspiraling objects or supernova explosions. These detectors are based on Michelson-like interferometers reaching sensitivities for lengths changes of better than 10 -18 m/√Hz. Currently, a second generation of gravitational wave detectors is under construction reducing relevant noise sources throughout their detection band by one order of magnitude. First steps towards a third generation detector - having two orders of magnitude larger sensitivity compared to the first generation - have been made. This gravitational wave observatory - the Einstein Telescope - is a European-wide effort leading to a sophisticated design including an optimum site selection. We present the status of these activities and give an overview of the state of the art technologies needed to realize such an instrument.