Galactic plane surroundings of the W43 molecular complex as seen in H i (color) and ¹²CO 1–0 (contours) integrated over 60−120 km s^-1, the complete velocity range of W43. The contours go from 40 to 200 K km s^-1 with a step of 20 K km s^-1, and are always monotonously increasing, never displaying ¹²CO dips (see Fig. 6b). The white boxes outline the extent of the W43 molecular complex (continuous lines) and its H i envelope (dashed lines) as defined in Nguyen Luong et al. (2011b). The black box locates the largest ring used in the R_H2 diagram (see Fig. 7) and the white cross its center. Stars pinpoint the red supergiant clusters/associations (RSGC2 and RSGC3) identified in the neighborhood.