Spatial distribution the Milky Way’s N_HI column density for V_LSR = −155 to +80 kms⁻¹ above a threshold of N_HI = 3 x 10¹⁹ cm⁻² with a maximum of 1 x 10²¹ cm⁻². Superimposed as contours is the spatial distribution of the Milky Way gas with excess optical extinction derived from the N_HI/A_V ratio (see text for details). The contours correspond to N_H2 = 5 × 10¹⁹ cm⁻² and to 1, 2, and 3 x 10²⁰ cm⁻². The LMC is located at l = 280°, b = -33°; the SMC at l = 302°, b = −44°. The yellow ellipse indicates the area observed with eROSITA.