Kauai is Hawaii's oldest inhabited island. Visitors can snorkel or whale watch along the beautiful Na Pali Coast. Mount Waialeale is one of the wettest spots on earth. Waimea Canyon (pictured here) is known as the Grand Canyon of the Pacific because it stretches 10 miles long and 3,600 feet deep. The gorge was created roughly 4 million years ago when a section of the Kauai volcano collapsed in on itself. (PHILIPPE BOURSEILLER—GETTY IMAGES)