  Observations of the powerful radio galaxy 1138-262 at z=2.2 suggest that this
galaxy is a massive galaxy in the center of a forming cluster. We have imaged
the field of 1138-262 with the Very Large Telescope in a narrow band
encompassing the redshifted Lyman alpha emission. We detect 34 probable line
emitters in the 6'x6' field. These are candidate Lyman alpha emitting galaxies
in the supposed cluster. The observations also reveal that the radio galaxy is
enclosed by a very extended Lyman alpha halo (160 kpc).
