Manoa is both a valley and a neighborhood that's part of Honolulu. It's about three miles from downtown, and less than a mile from Waikiki Beach.
The Manoa Valley neighborhood is largely residential, though there is also a university campus here, and is surrounded by the tall, green mountains of the Ko'olau Range. In the 19th century, Manoa was the setting for Hawaii's first sugarcane and coffee plantations.
Because of the geography and position of the Manoa Valley, it rains at least a little bit almost every day – rainbows occur frequently – and it is always incredibly lush. One of the main attractions is the 150-foot Manoa Falls.
Manoa Falls is only reachable after a hike of roughly 0.8 miles. It's a moderate trail, and most people can make the trip there and back in about an hour.