The 66A is part of the route that connects the town Baile Hercule with Petrosani. From Baile Hercule, the route starts on the 67D, which is paved.
At a point, the 67D splits into 66A, that continues towards Vulcan, and Petrosani. From that point, it is a gravel road, except for a part that is just east of the dam, which is old concrete blocks. They are easy to ride, but bumpy. The road north of the lake stays wet for a while after rain.
Coming from Petrosani, the first part, through the towns, are paved.
Of the 136 km, approx 57 is gravel.
It is conveniently connected to the 7A through Petrosani, if you are also planning on riding the Transalpina route.