Configuration of Gaia21blx in the Milky Way. The colored spirals represent (from left to right) the Perseus arm (green), the Local arm (blue), the Sagittarius arm (orange) and the Centaurus arm (red). In the figure, the Galactic center is represented by the black disk, while the lens and source for the C+ model are represented by the brown and purple disks, respectively. For the W− model, empty circles have been used (same colors as in the previous case). The Sun is the darker yellow point. X and Y are the Cartesian coordinates in the Galactic plane, centered at the Sun, with the X axis positive toward the Galactic center and the Y axes directed along the rotational curve. The configuration is computed following the work of Castro-Ginard et al. (2021).