Well, I'm not at home right now, but I can try to explain...
You exit the lighthouse. You face the lake. Turn left and get down the wooden ramp. Okay. Now walk against the natural wall, and at a certain time, you'll have a very steep slope. Walk to the top of it, jump if it helps. Now cross the natural road and you'll face another steep slope again. Get to the top of it. You're there !
This slope is so steep that you might be able to throw people over the hole that it makes... If Jimmy jumps over it, he'll splat to the ground.