Is it a Colossal Cavern?
Not to tell you your business, but I have a feeling that the more common verbal expression involves a sizeable chasm rather than a cavern.
It might be descended from the bible story about Lazarus and Dives - this probably isn't "died then got better" Lazarus but someone else with the same name - who found themselves on opposite sides of a particular chasm. Dives was in Hell, and Lazarus was in Heaven - one of the joys of which seems to be to look over to Hell and see people that you know. So the chasm is between heaven and hell. You're nominating Amazon cloud as heaven. Or, anyway, Microsoft cloud as hell.