Ruby Cavern
The Ruby Cavern is the ruby-lined cave behind the Great Waterfall into which the Scarecrow was swept.
First named in The Scarecrow of Oz, ch. 23
among them they partly carried and partly dragged the damp Scarecrow out of the Ruby Cavern, along the tunnel, and up the flight of rock steps.
Where this is
placed In Oz worked out
read out of the chapters cited on this page, not stated in any one sentence of them
Behind the Great Waterfall, which Scarecrow of Oz ch22 calls 'the Great Waterfall' by 'our Oz people,' reached after the party had already crossed back into the Land of Oz proper from Jinxland.