  We describe a large family of nonequilibrium steady states (NESS)
corresponding to forced flows over obstacles. The spatial structure at large
distances from the obstacle is shown to be universal, and can be quantitatively
characterised in terms of certain collective modes of the strongly coupled many
body system, which we define in this work. In holography, these modes are
spatial analogues of quasinormal modes, which are known to be responsible for
universal aspects of relaxation of time dependent systems. These modes can be
both hydrodynamical or non-hydrodynamical in origin. The decay lengths of the
hydrodynamic modes are set by $\eta/s$, the shear viscosity over entropy
density ratio, suggesting a new route to experimentally measuring this ratio.
We also point out a new class of nonequilibrium phase transitions, across which
the spatial structure of the NESS undergoes a dramatic change, characterised by
the properties of the spectrum of these spatial collective modes.
