Arch of Aroden
This monolithic ruined bridge spans the Straits of Aroden separating Avistan from Garund. The arch rises several hundred feet above the straits and stretches more than 15 miles to connect Corentyn in Cheliax with Chalshotur Qasr in Kharijite. Roughly a third of the immense and ancient structure has collapsed, making it useless as a bridge.
Sources: Pathfinder Chronicles Campaign Setting