A document describes tower cranes, including their assembly which involves airy work up high, their usage for raising buildings and doing bridge and port work, and seeing the world from their elevated perspective like a bird's eye view.

1. TowercraneBy Steinar Johansen

2. CraneassemblyAssembling a craneAirywork

3. Up in the worldThe viewBird’sperspective

4. UsageRaisingbuildingsBridge workPorts