  Events such as GRB130606A at z=5.91, offer an exciting new window into
pre-galactic metal enrichment in these very high redshift host galaxies. We
study the environment and host galaxy of GRB 130606A, a high-z event, in the
context of a high redshift population of GRBs. We have obtained multiwavelength
observations from radio to gamma-ray, concentrating particularly on the X-ray
evolution as well as the optical photometric and spectroscopic data analysis.
With an initial Lorentz bulk factor in the range \Gamma_0 ~ 65-220, the X-ray
afterglow evolution can be explained by a time-dependent photoionization of the
local circumburst medium, within a compact and dense environment. The host
galaxy is a sub-DLA (log N (HI) = 19.85+/-0.15), with a metallicity content in
the range from ~1/7 to ~1/60 of solar. Highly ionized species (N V and Si IV)
are also detected. This is the second highest redshift burst with a measured
GRB-DLA metallicity and only the third GRB absorber with sub-DLA HI column
density. GRB ' lighthouses' therefore offer enormous potential as backlighting
sources to probe the ionization and metal enrichment state of the IGM at very
high redshifts for the chemical signature of the first generation of stars.
