The Waterfall Mine is a type of location in Harvest Moon: Back To Nature.
Time stops while in the mine. There are 10 randomly generated floors. Each floor is traversed by uncovering a hidden ladder using the Hoe. Ladders never appear on the outer rim tiles, and the hidden ladder will be in the area of the room diagonally opposite to the one you just climbed down. To exit, climb up the ladder on the current floor. Exiting will automatically send you outside the mine.
A Power Berry can be randomly dug up on any of the 10 floors.