The Unterburg trolleybus turntable () is a disused turntable for trolleybuses in the Solingen district Burg an der Wupper. The facility was regularly used by trolleybus line 683, operated by the Stadtwerke Solingen (SWS), until 15 November 2009, but is preserved in working condition. The turntable is the last of only four turntables of this type in the world. Two more were located in Great Britain: the Christchurch trolleybus turntable (1936 to 1969) and the Longwood trolleybus turntable at Huddersfield (1939 to 1940). The fourth trolleybus turntable, in Guadalajara, Mexico, was in use from 1982 to 1983 and from 1985 to 1988. Description The turning process lasts 45 seconds and is always carried out without passengers on board. The turntable is remotely operated by the driver from an adjoining control house. The trolley poles are lowered manually before starting the rotation and are reattached to the trolley wires afterwards, with the aid of so-called "threading tufts". History Until 1959, the independent municipality of Burg an der Wupper was connected to the neighbouring cities of Solingen and Remscheid by tram lines 3 and 4. A separate bridge over the Wupper connected the two tram lines. That was destroyed in World War II and not rebuilt. Instead, a stub-end terminal was placed on the Solingen side. The tram system was shut down in 1959 and replaced by a trolleybus line. The narrow valley of the Wupper did not leave enough space for a turning loop on the -long, but only -wide transfer stop on the tramway. The confined area between the river and a steep slope proved particularly problematic. Therefore, as with the two above-mentioned turntables in the UK, a circular disc-type turntable, with a diameter of , was installed to turn trolleybuses on line 3. That was sufficient for the ÜHIIIs trolley type, which was exclusively used at that time. Originally, the mechanism was manually operated by the driver by means of a hand crank. Introduced in 1968, the new -long vehicles of the three-axle Trolleybus Solingen (TS) type could not be used on line 3, which was why only the long-outdated ÜHIIIs vehicles were used until 27 December 1974, after which the turntable had an extension attached so it could also be used by the TS models. In 1985, the turntable was completely renewed, being extended to in diameter. Because of the limited size of the Unterburg turntable, line 683