North of Lihue and Kapa'a on Kauai, the old dirt road from Kealia Beach past Donkey Beach and on to Anahola is a popular 4 mile route. There are several side dirt roads and single tracks to explore.
To reach the mountain biking trailhead from Lihue, head north on SR56 (Kuhio Highway) to Kapa a. Continue north for 1.5 miles to the Kealia Beach parking area (between milepost 9 and 10). Start riding north on the old road towards Anahola. Generally, stay to the right when the trail forks. After the first mile when the road seems to end in a small valley, turn right and head down across the stream and continue right on singletrack. When this singletrack ends in another small meadow, turn hard right to gate and continue through brush to pickup the road again. The route can be tough to follow at times, but generally stay on the main route and dont climb up side roads or head down side road, if you want to get to Anahola. The side roads are cool to explore on the way back.
Overall, Donkey Beach - Kealia Trails is the 8th most popular mountain bike trail of all 22 mountain biking rides in Hawaii.