The European XFEL is a large x-ray free-electron laser facility already operating in the Hamburg area of Germany. It is designed to provide a transversally fully coherent x-ray radiation with outstanding characteristics in terms of high repetition rate, short wavelength, short pulses and and high average brilliance. The three main beamlines are operating or under final commissioning. The extraordinary characteristics of the beam are coming at the cost of many challenges for high precision optics and mechanics. We will describe the project, taking some particular examples of the present and future challenges.