  We study the properties of two bars formed in fully cosmological
hydrodynamical simulations of the formation of Milky Way-mass galaxies. In one
case, the bar formed in a system with disc, bulge and halo components and is
relatively strong and long, as could be expected for a system where the
spheroid strongly influences the evolution. The second bar is less strong,
shorter, and formed in a galaxy with no significant bulge component. We study
the strength and length of the bars, the stellar density profiles along and
across the bars and the velocity fields in the bar region. We compare them with
the results of dynamical (idealised) simulations and with observations, and
find, in general, a good agreement, although we detect some important
differences as well. Our results show that more or less realistic bars can form
naturally in a $\Lambda$CDM cosmology, and open up the possibility to study the
bar formation process in a more consistent way than previously done, since the
host galaxies grow, accrete matter and significantly evolve during the
formation and evolution of the bar.
