Projection on the Galactic plane of the locations of clusters with derived parameters, colour-coded by age. Top panel: all ages. The shaded area shows the spiral arm model of Reid et al. (2014). The dashed arm is the revised path of the Cygnus arm in Reid et al. (2019). Bottom row: splits the sample into three age groups. The Sun is at (0,0) and the Galactic centre is to the right. The most distant objects were left out of the plot.