One of the interesting features is Phantom Ship. It's part of an old lava dike that forms a spur climbing the rim of the caldera. I want to say it's two football fields long, but it might be only one; it's about nine stories high.
If I were going to hide a sword that a Once-And-Future King might need to find, I would hide it on the Phantom Ship in Crater Lake.
I'm not sure where I'd put the monorail, though.