How did the Bridge of Death get there in the first place?

Gratuitous Python in service of a serious question:

Bridges like the Bridge of Death (I don't know what that kind of bridge is called - I keep thinking suspension bridge but that's like the Golden Gate Bridge) are a mainstay of the historical adventure/fantasy genre.

But how would they build a bridge like that in the first place? How do they attach it to both ends when there's no way to get across in the first place?