The best secrets are often hiding in plain sight. A waterfall tucked just off a road you have driven countless times. A viewpoint on a hill you have passed but never thought to climb. A quiet campsite in the countryside with a hiking trail only the locals know.
Then one day you take a wrong turn, your nephews ask you to take them for a walk, or a friend mentions a place you have never heard of, and you go and wonder, "How do people not know about this place?"
