  We calculate in heavy baryon chiral perturbation theory the local
NN-potentials generated by the two-pion exchange diagrams at two-loop order. We
give explicit expressions for the mass-spectra (or imaginary parts) of the
corresponding isoscalar and isovector central, spin-spin and tensor
NN-amplitudes. We find from two-loop two-pion exchange a sizeable isoscalar
central repulsion which amounts to $62.3 $MeV at $r=1.0 $fm. There is a
similarly strong isovector central attraction which however originates mainly
from the third order low energy constants $\bar d_j$ entering the chiral $\pi
N$-scattering amplitude. We also evaluate the one-loop $2\pi$-exchange diagram
with two second order chiral $\pi \pi NN$-vertices proportional to the low
energy constants $c_{1,2,3,4}$ as well as the first relativistic 1/M-correction
to the $2\pi$-exchange diagrams with one such vertex. The diagrammatic results
presented here are relevant components of the chiral NN-potential at
next-to-next-to-next-to-leading order.
