SeattlePI has an article describing the loop in more detail. The last time I drove the loop I didn't get very far. A few miles after taking the exit to highway 530 I found a beautiful barn set against some pines and snow capped mountains at sunrise. When I stopped to take a picture of the barn, I noticed this beautiful ornate spider web glistening in the rising sun.
Before you leave check to make sure that the roads are open - part of the loop gets closed in winter.