VLT/FORS1 2D spectrum obtained after the optical afterglow of GRB 070721B faded. The photometric counterparts of the different traces are labelled according to Fig. 6 and Table 4. The host (D4) is only visible via its Lyα emission. The afterglow spectrum of GRB 070721B would be located at the position of D4. Prominent absorption and emission lines of the galaxies and intervening absorption-line systems are highlighted and colour-coded. The intervening DLA present in the afterglow spectrum is the very bright galaxy D3. The spectrum of the Lyα emitter D7 displays an intervening DLA as well.