"The problem is, we discovered how to control the human brain in
   totally arbitrary ways, build and grow new ones, squish them together,
   etc etc, but we also discovered how to make new physical laws, teleport
   things, make matter at a distance, etc etc.  And we were fighting
   secret military battles while we did it.  So now we can't quite tell
   which one we are doing, for sure: giving your brain an exotic light
   show, or actually making that exotic light show around you.  Still, the
   park is broken into two categories: unbelievable experiences of the
   mind, and provable experiences of reality that your mind will never
   believe is real.  The first question is, what do you need to experience
   to know that the physical things, which are actually real, aren't one
   of the neurological tricks?"
   visitor A: "I believe you!  Show me whatever!"
   The gyrating bundle of organs and exotic matter with a floating park
   badge looks at visitor A dismissively.
   visitor B: "I'd like to take this videocamera with me that streams
   video to a blockchain."
   Park representative: "Great, we don't even have to give you one of our
   own.  Both of you, come this way."