Iao Valley State park is one of Maui's most popular tourist attractions. The park is near the center of the extinct West Maui Mountains volcano crater. Dramatic mountain ridges surround the lush park. The summit ridge at the valley's head is the second wettest location in Hawaii, receiving an average of 386 inches of rain per year. All this water flows down the Iao stream. Inside the crater is a very distinctive ridge that rises 1200ft above the valley floor called the Iao Needle. There's a lot of interesting history associated with the park which the Tour Guide will tell you about.
There's about half a mile of paved trail inside the park. There are also other unmarked trails inside the park around the stream. If you enjoy hiking come prepared to do some exploration. The stream side trail that most tourists don't explore will show itself to you as you walk the park.