Very rough asphalt, with some severe damage. The scenery, however, is fantastic.
The climb isn't challenging. At the end, you can either turn around or, if the weather is really dry, continue on the gravel MTB trail. I decided to keep going because I pretty much ride everything on my road bike (now with 28/30mm tires). It was worth it, but it was really tough, and I wouldn't go any further a second time; I'd turn around instead. The route up the mountain is a lot of fun, though; I'd do it again anytime.