There are Shy Guys and Flaptors, birds who'll fly around and dive-bomb if Captain Toad gets too close, here. Walk down the ramp and you'll see a couple of holes in the side of the hill. Go through the left one for the first gem, as well as coins and a Mushroom. Stand inside the touchstone and touch it to raise it. Walk up the ramp to the level of the Shy Guys. Kill them all with turnips for the second gem. Drop down the ladder by the Flaptor for a 1-up. Walk around and you'll find more touchstones. Touch the third one to drop it so you can reach the third gem under the grass. Stand on the fourth touchstone's ramp and touch it to raise it to the level of the Star.
Special Challenge: Defeat all enemies.