Crew members in foreground looking up at Tower Crane in back ground as it disassembles itself.
To disassemble themselves, tower cranes construct derricks on the rooftop of the finished project. (Derricks are tower cranes' simpler great-granddaddy.) These derricks then help dismantle the tower cranes, and—in the case of internal climbers—lower their parts one by one to the ground using extremely long cables