  High redshift radio galaxies (z>2) are believed to be progenitors of the
giant ellipticals of today. They are often associated with giant Ly-alpha
nebulae (sometimes >100 kpc), which have been for more than two decades
valuable sources of information about the evolutionary status of the host
galaxy and its chemical enrichment and star formation histories.
  I present in this paper a summary of the most relevant results about the
giant nebulae obtained in the last ~10 years and the implications on our
understanding of the early phases of evolution of massive elliptical galaxies.
