See ~35 years ago

All I remember is a giant metal robot guarding a hill.  Somehow the group was able to get past the robot and into a cave behind or underneath the machine.  The group spoke to the machines keeper and then noticed an entrance to another chamber behind a pile of junk. (The chambers door was blocked by junk).  Past the door was a large cave where the group found a white flower growing on a small hill in the center of the cave.

That’s all I remember.