Firth of Fourth - some infos please!

Hi!
I was searching infos about Firth of Fourth... And I find that infos:
- Firth of Fourth is city near Edinborough.
- Firth of Fourth is a river.
- Firth of Fourth is a bridge

I want to know the true, and if somebody can put here a little bit infos, history of Firth of Forth, and some photo... I will be very thankful!

Greetings