Crane Question

[Coke6pk]

Was driving home from Ottawa this weekend, and as I came into Toronto there was a highrise condo building under construction that caught my eye.  What appeared to be sitting on the roof of the building was the long crane unit I am used to seeing on the top of the tall "scaffolding".  [I'm sure I will use lots of incorrect / non-technical terms]

This got me thinking... I've seen cranes go up, but this got me wondering... how does that big boom get down?

I will let the smart folks here teach me....

Coke

[timc]

I think the answer is: the opposite of how it got up there. :-)

Seriously, though, the internet tells me that you use the large crane to lift a smaller crane up, which is used to disassemble the large crane lower the pieces down. And then you bring up an even smaller crane to disassemble and lower that one. And the third one is small enough to be taken apart by hand and the pieces taken down via the inside of the building.

I know for shorter buildings they would use a crane from the ground, but I haven't seen this done on high rises before.