Averaged spectra of the structures along the ring of RCW 120, sorted by the regions indicated in Fig. 2 (ring, southwestern PDR, southeastern PDR and northeastern PDR). Left panels: averaged [¹²C II] and scaled up [¹³C II] emission by the local abundance ¹²C/¹³C-ratio of 59. Right panels: averaged ¹²CO and ¹³CO (3 →2) emission. The black data points with error bars indicate the velocity resolved optical depth.