The Penobscot Bridge site is home to the Penobscot Narrows Observatory, the first bridge observation tower in the United States and the tallest public bridge observatory in the world.
The very interesting thing about the bridge is its construction. The cables are sheathed in 16″diameter hard-plastic protective tubes.
Each steel strand is coated with epoxy where the epoxy fills the spaces inside the strand as well as coating the outside.
Finally inside each plastic tube is filled with an inert gas that allows the internal pressure to be monitored by computer, which will verify that the pipe is not leaking and eliminates all oxygen from the cable-stayed environment.
This construction means that if the tubing should be compromised, the cable will not corrode because the strand is in a nearly oxygen-free environment.
This design also means that individual cables can be easily replaced or upgraded without disturbing traffic or compromising bridge safety.