ABSTRACT
This chapter presents a brief story of how Federigo Enriques was led to the discovery of Enriques surfaces. The double plane construction of Enriques can be modified by considering a morphism of degree 2 onto some other rational surface. This can be obtained by applying some birational transformations to the plane. Thus one may consider any Enriques surface as a double cover of a quadric or as a double cover of a 4-nodal Del Pezzo surface of degree 4. Enriques proved that a general Enriques surface can be obtained as a quotient of a K3-surface by a fixed-point-free involution. Enriques was the first who observed that a general Enriques surface admits infinitely many birational automorphisms.
