In port cities accurate timekeeping always played an important role for navigation and for the exact determination of the longitude at sea. The first time ball was erected in Greenwich observatory in 1833. Around 200 time balls were built worldwide, and about 60 still exist, many in English-speaking countries. In the German Empire time balls were erected in cities along the coast of the North Sea and the Baltic, the first in the Imperial Naval Observatory in Wilhelmshaven (observatory 1874-1905, port 1905), then in Cuxhaven (column 1875-1929/1934), Bremerhaven (time ball column 1876-1928/1948, port office 1895, lighthouse), Bremen (port office 1895), Emden (port 1911), Kiel (observatory 1884, Imperial Wharf 1886, artillery warehouse 1908), Swinemünde (now Swínoujscie, Poland, column 1879), Stettin (Szczecin, government building 1908), Danzig-Neufahrwasser (Gdansk Nowy Port, Poland, pilot tower 1876-1894, lighthouse 1894-1929, 2008) and Qingdao (Tsingtau, observatory 1898, time ball 1909). The time ball in Hamburg on the top of the Imperial Warehouse, made by Carl Bamberg of Berlin in 1876, had a complicated construction. After a fire it was rebuilt in 1893 (diameter of the time ball 1.5m, 53m high); it was in use until 1934 and demolished in 1967. The time was determined by observing meridian transits of stars in Hamburg Observatory with the Repsold meridian circle and transmitted to the time balls, first through an electric cable, then in Hamburg already since 1910 by radio technology (Norddeich Radio Station). In 1919 a time service was started in the German Hydrographical Office (Deutsche Seewarte) in Hamburg; the Cuxhaven and Bremerhaven time balls were taken over and regulated by this office beginning in 1929 and were thus no longer managed by the local observatory. A very detailed model of the Hamburg time ball (1:10) was made in 2011.