  In this contribution we will present deep VLT spectroscopy observations of
the giant emission line halo around the z=2.49 radio galaxy MRC 2104-242. The
morphology of the halo is dominated by two spatially resolved regions. Lya is
extended by >12" along the radio axis, C IV and He II are extended by ~8". The
overall spectrum is typical for that of high redshift radio galaxies.
Interestingly, N V is present in the spectrum of the region associated with the
center of the galaxy hosting the radio source, the northern region, while
absent in the southern region. Using a simple photoionization model, the
difference in N V can be explained due to a metallicity gradient within the
halo. This is consistent with a scenario in which the halo is formed by a
massive cooling flow or originates from the debris of the merging of two or
more galaxies. However, also other mechanisms such as jet-cloud interactions or
starburst-winds could be important.
