Phew, this is a tough one to describe. But let’s get something straight—what you see at the top is probably something called the slewing unit and various other parts, not scaffolding.
    To construct a tall building a climbing tower crane is used. As the building gets taller, so does the crane. How is this done?
    Okay, let's talk about how the crane is kept in place first: the construction company pours a huge concrete slab. The crane’s base is bolted to this and is rock steady.
    On top of the base is the “mast” (the steel tower). On top of the mast is the “slewing unit”—the gears and motor that rotate the crane. On top of the slewing unit are the operator’s cab; the “jib” (the horizontal arm that does the work); the machinery arm that contains the electronics and motors that lift the loads; and concrete counterweights.
    To assemble the tower crane a mobile crane is used to erect two six metre sections of the mast and a section called a climbing frame. These rise from the base. On top of this latticed tower structure, the mobile crane places the slewing unit, the jib, machinery arm, and the counterweights.
    The tower crane is on its own now. It reaches high into the sky by itself, one mast section at a time. To accomplish this, hydraulic rams (insanely strong jacks) lift up the climbing frame and everything on top. A six metre space is opened up for the crane to insert another section of mast, which is then bolted into place. This goes on and on until the tall building is finished. The crane then dismantles itself, one section at a time.