Crystal Cave is a map, which seems to be in a cave full of different colored crystals, it is quite easy to triumph on.
Long and shiny. However, the best place to camp is the area closer to the exit. Heights here are mostly hard to find. You can however be good if you spam at right places.
As of the Mega Update (10/13/19) It has been removed from the game and no announcements have been made to signify that it is returning to the game.