To the cycling enthusiasts I went with, the "old" path up to the castle was no problem, but if you are older, short, out of shape or have bad knees, make sure you take the new path. It is wide, paved most of the way and has interpretive signs along the way. I can't say that it is any steeper because it goes to the same place, but it is a slope rather than some combination of rough, uneven stone stairs, tree roots and the occasional hillside scramble. Those afraid of heights should not be too concerned either way, and the old way does have an occasional view of the river, but the views are best from on top the castle, where the fear of heights can become a problem – another good reason to at least go DOWN the new way, as I did.
As you face the town from the river, the new path is on the right hand side of town and plainly marked. The old way starts in the middle of town, down the old Main Street to your left. Your choice. Either way, leave plenty of time to get up and back before dark, but if you have the opportunity, stay into the night and see the beautiful way the old castle is illuminated.