Left:3D view of a triaxial ellipsoid used to help visualizing the generic geometry and symmetry axes of the fish bowls (Fig. 14) as described in Sect. 4.5. Middle: schematic view of the north fisw-bowl (FB_N) cut by a plane through the los and the || line (i.e., the red ac-plane as represented in the top panel) and adopting c = b = 3.′′8. Right: relation between the size of the c-axis of the fish bowls and its los-inclination consistent with the morphology and radial velocity gradient observed in our ALMA CO maps). The vertical and horizontal line marks the values of c and i_c that reproduce the observations and are consistent with a formation time ~650 ± 100 yr.