Ko'olau Forest Reserve

Hold on to your hat - now the real fun begins! As the highway snakes along the edge of the Ko'olau Forest Reserve, the jungle takes over with a one-lane bridge and waterfall offering drama at every other bend. Ko'olau, which means 'windward,' catches the rain clouds and squeezes out about 80in of rain annually on the coast and a mighty 200in to 300in up the slopes. No surprise - that makes for awesome waterfalls as the rainwater rushes down the reserve's abundant gulches and streams.

Paralleling the highway is the Ko'olau Ditch, a century-old system that carries up to 450 million gallons of water a day through 75 miles of ditches and tunnels from the rain forest to the dry central plains of Maui. If you want to take a closer look, stop at the small pull-off just before the bridge that comes up immediately after the 8-mile marker. Just 50ft above the road you can see a hand-hewn stone-block section of the ditch on your right.

After the village of Kailua, home to the workers who maintain the ditch, you'll be treated to a splash of color as you pass groves of painted eucalyptus trees with rainbow-colored bark.