  We compute properties of the interface of the 3-dimensional Ising model for a
wide range of temperatures, covering the whole region from the low temperature
domain through the roughening transition to the bulk critical point. The
interface tension sigma is obtained by integrating the surface energy density
over the inverse temperature beta. We use lattices of size L x L x T, with L up
to 64, and T up to 27. The simulations with antiperiodic boundary conditions in
T-direction are done with the Hasenbusch-Meyer interface cluster algorithm that
turns out to be very efficient. We demonstrate that in the rough phase the
large distance behavior of the interface is well described by a massless
Gaussian dynamics. The surface stiffness coefficient kappa is determined. We
also attempt to determine the correlation length xi and study universal
quantities like xi^2 * sigma and xi^2 * kappa. Results for the interfacial
width on lattices up to 512 x 512 x 27 are also presented.
