Gavmishan Bridge - Credit: Wikimedia Commons
Gavmishan Bridge is a historic bridge in Darreh Shahr County, Ilam Province, Iran. The bridge was built in the late Sasanian era on Karkheh River, parts of which constitute the modern-day border of Ilam and Lorestan provinces. It is in length and about in width. It has the longest arch span among the ancient bridges in Iran and the world. Many experts consider it an engineering feat, considering the time when it was built, the material used and the floods it has withstood during its age of 1,400 years. Read more on Wikipedia
Source: en.wikipedia.org