Most medium and large cities have a streetcar (tram) system, sometimes fairly extensive. In some areas, streetcar lines run underground in the central city area. Trams are especially prevalent in many eastern German cities.
Most systems have been modernized with sleek new rolling stock and many systems now carry the Trambahn moniker. Service is fairly frequent, usually 20-30 minutes during off-peak periods.
Streetcar stops throughout Germany are marked with this sign: