system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: when a huge skyscraper is built, how do they get the cranes and construction equipment down from the top when complete?
gpt
Each situation is different... but it's usually some version or combination of one of these basic methods: 

1) The "big" crane is dismantled and brought to the ground by a smaller crane. Compared to the building parts they lift... cranes are relatively lightweight in small pieces... so they can be carried by smaller/mobile cranes.

2) Same concept but the big crane is disassembled and lowered using its own structure or the building as a support system.

3) (less common) The bulk of the crane support is designed into the guts of the building and is essentially abandoned... or there actually is no "tower" and the crane is simply lifted as the building goes up so there is very little to take down at the end of the job.