  Using the Quantum Inverse Scattering Method we construct an integrable
Heisenberg-XXZ-model, or equivalently a model for spinless fermions with
nearest-neighbour interaction, with defects. Each defect involves three sites
with a fine tuning between nearest-neighbour and next-nearest-neighbour terms.
We investigate the finite size corrections to the ground state energy and its
dependence on an external flux as a function of a parameter $\nu$,
characterizing the strength of the defects. For intermediate values of $\nu$,
both quantities become very small, although the ground state wavefunction
remains extended.
