  The properties of center vortices are discussed within continuum Yang-Mills
theory. By starting from the lattice theory and carefully performing the
continuum limit the gauge potential of center vortices is obtained and the
continuum analog of the maximal center gauge fixing is extracted. It is shown,
that the Pontryagin index of center vortices is given by their
self-intersection number, which vanishes unless the center vortices host
magnetic monpoles, which make the vortex sheets non-oriented.
