  Subradiant excitations, originally predicted by Dicke, have posed a
long-standing challenge in physics owing to their weak radiative coupling to
environment. Here we engineer massive subradiance in planar metamaterial arrays
as a spatially extended eigenmode comprising over 1000 metamolecules. By
comparing the near- and far-field response in large-scale numerical simulations
with those in experimental observations we identify correlated
multimetamolecule subradiant states that dominate the total excitation energy.
We show that spatially extended many-body subradiance can also exist in
plasmonic metamaterial arrays at optical frequencies.
