Distribution of high-altitude (| z | > 400 pc) clusters with positive and negative Galactic latitudes (black and red/grey, respectively). Dots indicate clusters older than 1.0 Gyr while crosses correspond to lower ages. Data were taken from Heiter et al. (2014), Paunzen & Netopil (2006), Netopil et al. (2012). The four old clusters at highest metallicity are marked by the four black dots to the right (in order left to right: NGC 2420, M 67, NGC 188 and NGC 6791.