Just a conversation between two cyclists:
"The Col de l'Iseran is the highest road in Europe."
- No way, that's the Bonette.
"The Tiefenbachferner is even higher."
- It isn't.
First, we must be precise about what we mean by "the highest road." Considerations include:
Photo: Col de la Bonette
Let's examine the usual contenders. Based on altitude, the Bonette at 2802 meters appears higher than the Iseran (2770m). However, the last kilometer is a loop to the highest point, the so-called Cime. The col at 2715m is slightly lower than Iseran's summit. So, the Bonette is the higher road, while the Iseran is the higher col, according to the French definition of a col:
According to the official French definition, a col (a mountain pass) is the highest point of the road, located between two higher mountain peaks. According to that definition, you must be able to drive down on both sides of the col and walk up from the road on two sides. (source: 100cols.com)
In the category of the highest paved col in Europe, the Iseran is indeed number 1. However, if we consider dead-end routes, the title goes to the infamous Tiefenbachferner in Austria, with the highest point right as you exit the tunnel at 2829 meters.
Photo: Tiefenbachferner, near Sölden.
However, this comparison only applies to the Alps. Spain boasts the uncrowned king of Europe, the Pico Veleta in the Sierra Nevada, reaching 3375 meters. The road quality decreases as you ascend, becoming completely unpaved above 3250 meters. Here lies the highest paved road in Europe, though the last stretch is more suitable for a gravel bike.
Highest paved col in Europe: Col de l'Iseran
Highest fully paved road in Europe: Tiefenbachferner
Highest partly paved road in Europe: Pico Veleta.
Highest through road in Europe: Cime de la Bonette