East of Princeville and northwest of Kapa'a on Kauai, the Wai Koa Loop Trail is a 5 mile loop on the private Wai Koa Plantation. The trail is popular with families heading out to mountain bike, but also keep an eye out for hikers and trail runners.
Since this is public access to private property, please stay on the designated trail and do not pick any fruits or vegetables. The Wai Koa Loop trailhead is located on the mauka side of Kuhio Highway in Kilauea at Anaina Hou. It is located about 0.25 miles west of the turn-off to the Kilauea Lighthouse turnoff from the highway. There is mountain bike rental available at the nearby Kauai Miniature Golf facility (11am-6pm).
Overall, Wai Koa Loop Trail is the 19th most popular mountain bike trail of all 22 mountain biking rides in Hawaii.