  We evaluate the Raman light scattering intensity for the square lattice
Heisenberg antiferromagnet with plaquette ring exchange J_\Box. With the
exchange couplings as fixed before from an accurate fit to the spin-wave
dispersion in La2CuO4, leading in particular to J_\Box=0.24J, we demonstrate in
a parameter free calculation that the inclusion of the plaquette exchange
contribution to the dispersion and the magnon-magnon interaction vertex gives a
peak position in $B_{1g}$ scattering geometry E_max = 2.71J which is in
excellent agreement with the experimental data. Yet, the intrinsic width and
the lineshape of the two-magnon remain beyond a descriptions in terms of a
spin-only Hamiltonian.
