Most cliffs are not actually cliffs. They are doors that slowly open. Or are locked. Telephones that ring. Or don't work. People who arrive in the middle of the night. Or who miss their trains. In other words, they are ordinary occurrences that writers must somehow make extraordinary.
How do we do that?
Atmospherics help. There's a reason it's often a "dark and stormy night."
Backstory can be useful. Every location is haunted by some sort of history.
I also remind myself that stories are about what's possible---not what's probable. I try not to let the structure of my story be locked up tight. I always leave space for something unexpected. If it surprises me, I know it will delight my readers.
Leave a door open--just a little bit. You never know what might come in.