Kingdom Builder: Caves, a promotional item from Queen Games for Spiel 2012, consists of four cave tiles and rules.
On each quadrant, put one of the cave tiles on any mountain hex, which is not within two hexes of a location, castle or nomad hex. A cave counts as a mountain hex.
Once every turn, before or after the mandatory action, the player may move one of his settlements adjacent to a cave, to any empty and suitable hex adjacent to any cave (including the same one) on the board.