Distribution of clusters of the MWSC survey projected onto the Galactic XY-plane. Blue dots are open clusters and associations, red triangles mark globular clusters. The dotted circle shows the border of the Galactic disk (diameter ~20 kpc) as indicated by distant open clusters. The thick solid cyan and magenta sections of the spirals indicate the position of local spiral arms as defined by the COCD clusters (Piskunov et al. 2006). They are formally extended to the edge of the disk with thin solid curves. The light (yellow) thick circle around the Sun with radius of 1.8 kpc marks the completeness limit of the survey. A cross at (X,Y) = (8.5,0) kpc indicates the position of the Galactic centre.