The Mountains (like the Cliff) is a pretty empty place. Nothing will be here until the 9th of Spring in your second year. An earthquake will occur, unblocking the path up the mountain. You'll find a cave inside with the Nevermelt Ice inside.

Inside the cave you'll also find a sprite. There is a secret passage along the right-side of the cave with the little guy hidden in the very back. To keep his location a secret he'll give you a Power Berry.