Road M5

The M5 is a high mountain road located on eastern Bosnia and Herzegovina. It’s definitely not for anyone suffering from vertigo or a fear of landslides.

The road is gravel, narrow (impassable for 2 cars at the same time), open to all motorized vehicles. It follows the Canyon Praca through the Praca valley. It’s incredibly disorienting to look over the edge, or even just to see the valleys a couple thousand feet below you. It’s a mind numbing vertical drop of hundreds of meters so you might want to give it a miss on a windy day.
The road is 21.4km long. It runs over the old demolished Eastern narrow gauge railroad ("Ostbahn") of the country. Your wheels will be astounded at the wonderful views of the mountains spread out before you! They are terrible for drivers who are prone to vertigo. In many places the road is bordered by a drop of hundreds of meters (many hundreds of feet) unprotected by guardrails. The road includes several scary wooden bridges.
Pic: https://mw2.google.com/mw-panoramio/photos/medium/19357541.jpg