Multi-wavelength overview of the Diamond Ring. Spitzer/MIPS 24 μm (a) and 8 μm (b) and 4.88 GHz GLOSTAR (c) Effelsberg-only (145" beam) emission of the H II region associated with the Diamond Ring. Panel d) shows the ¹²CO 1→0 emission in the velocity range −8 to 3 km s⁻¹. The overlaid line integrated (−8 to 3 km s⁻¹) [C II] contour levels (40–120 K km s⁻¹ in steps of 20 K km s⁻¹) in all panels correspond only to the emission of the Diamond Ring (and not cluster Cl 13). The position of the ionising star #227 is indicated with a yellow star, the position of the protostars of Kryukova et al. (2014) are marked by magenta crosses in (c) and (d). They are amply visible in the 24 μm image. The south-western corner of the DR was not observed in [C II] as indicated by the gray line.