  Relativistic Hartree-Bogoliubov (RHB) theory in coordinate space is used to
describe the chain of even-even Zirconium isotopes reaching from Zr116 to the
drip line nucleus Zr140. Pairing correlations are taken into account by a
density dependent force of zero range. For neutron numbers larger than the
magic number N=82 a giant neutron halo outside the core of Zr122 is observed.
It is formed by up to six neutrons.
