These cities are not listed in the main menu. Some of them have metro-like systems, others may get metros in the future or had them in the past. Some of the pages are nearly empty, while other pages already contain considerable resources like logos, photos, announcements, or maps. Adelaide, Dublin, Liverpool, Portland, Rhine-Ruhr, San Diego, and Zurich are good examples. Rhine-Ruhr and Pearl River Delta pages are special: they are redundant pages with the only purpose to highlight clusters of metro cities.