  The production of $\Upsilon$ mesons in Pb-Pb collisions at a centre-of-mass
energy per nucleon pair $\sqrt{s_{\rm NN}}$ = 5 TeV is measured with the muon
spectrometer of the ALICE detector at the LHC. The yields as well as the
nuclear modification factors are determined in the forward rapidity region
$2.5<y<4.0$, as a function of rapidity, transverse momentum and collision
centrality. The results show that the production of the $\Upsilon$(1S) meson is
suppressed by a factor of about three with respect to the production in
proton-proton collisions. For the first time, a significant signal for the
$\Upsilon$(2S) meson is observed at forward rapidity, indicating a suppression
stronger by about a factor 2-3 with respect to the ground state. The
measurements are compared with transport, hydrodynamic, comover and statistical
hadronisation model calculations.
