Kauai is the oldest of the Hawaiian Islands, formed about eight million years ago when a single volcano rose out of the sea. All that remains of that eruption is the cone of Mount Waialeale. The 5,208 foot mountain is one of the wettest places in the US with 444 inches of rain yearly. Moisture-laden trade winds funnel rain clouds up the slopes of the ancient mountain. Over time, the rain has eroded gorges up to 3,000 feet deep, such as the Waimea Canyon.