Taroko began as coral deposits, compressed beneath an ancient sea and transformed by aeons of geology into limestone, then marble, schists and gneiss. Some five million years ago, Taiwan started lifting from the sea as the Philippine and Eurasian plates collided. Water erosion then carved out softer deposits to leave the towering canyon walls of harder rock.
This 18km marble-walled gorge is Taroko National Park's crown jewel. It's a must-see attraction whether you're hiking its trails, peering at its geological features or simply driving along the road that runs right through the middle (albeit much of the way in tunnels), wondering just how high are those mountains floating so vertiginously far above.