  We give an alternative construction of the Betti realization functor on the
derived category of motives of complex algebraic varieties via the category of
CW complexes instead of the category of complex analytic spaces. In particular
we show that the functor we define via the category of CW complexes coincide
with Ayoub's one. We deduce from this construction that Ayoub's realization
functor on geometric motives factors trough Nori motives and that the image of
this functor on the morphisms between the motive of a point and a shift of a
Tate twist of the motive with compact support of a complex algebraic variety
coincide with the classical cycle class map on higher Chow groups.
