Marble Mountain is a mountain that towers over Northern Island, and can be seen anywhere from the island. It is made of purple and gray rock, and has various zipline transports. Fans believe Marble Mountain is an homage to Hilltop Zone from Sonic the Hedgehog 2. There is a hidden caldera underneath, waiting to blow and turn Marble Mountain into a volcano.
Marble Mountain is relatively cool, and the air is crisp and clean. Act 2 is snowy and icy, but maintains the ziplines.