  We study the driven-dissipative steady-state of a coherently-driven Bose
field in a honeycomb lattice geometry. In the presence of a suitable spatial
modulation of the hopping amplitudes, a valley-dependent artificial magnetic
field appears and the low-energy eigenmodes have the form of relativistic
Landau levels. We show how the main properties of the Landau levels can be
extracted by observing the peaks in the absorption spectrum of the system and
the corresponding spatial intensity distribution. Finally, quantitative
predictions for realistic lattices based on photonic or microwave technologies
are discussed.
