  Very soon a new generation of reactor and accelerator neutrino oscillation
experiments - Double Chooz, Daya Bay, Reno and T2K - will seek for oscillation
signals generated by the mixing parameter theta_13. The knowledge of this angle
is a fundamental milestone to optimize further experiments aimed at detecting
CP violation in the neutrino sector. Leptonic CP violation is a key phenomenon
that has profound implications in particle physics and cosmology but it is
clearly out of reach for the aforementioned experiments. Since late 90's, a
world-wide activity is in progress to design facilities that can access CP
violation in neutrino oscillation and perform high precision measurements of
the lepton counterpart of the Cabibbo-Kobayashi-Maskawa matrix. In this paper
the status of these studies will be summarized, focusing on the options that
are best suited to exploit existing European facilities (firstly CERN and the
INFN Gran Sasso Laboratories) or technologies where Europe has a world
leadership. Similar considerations will be developed in more exotic scenarios -
beyond the standard framework of flavor oscillation among three active
neutrinos - that might appear plausible in the occurrence of anomalous results
from post-MiniBooNE experiments or the CNGS.
