Fairly flat once you're on the loop trail. Some slight up/downs. You can make it more challenging by going down to the lighthouse or doing multiple loops. Easy to get lost your first couple times visiting if you don't pay attention to the signs directing you to the various trails at every fork in the road. Some forks aren't marked clearly, so still good to pay attention (look for others coming toward you to help choose the correct path). Still worth it, as you get some good western views of the Sound and Olympics.