Grand Canyon of the Pacific - Kauai, Hawaii
There is something special about a deep canyon within a relatively small Island. On the island of Kauai, Hawaii there is a deep canyon that is rugged, lush and remote. This trail wasn’t ultra distance, but it offered almost 3000 feet (1000m) of elevation gain over 8.5 miles (13.5 km) on an out and back. The trail down started with very deep washouts and then transitioned to single track through a dense forest. At the bottom, the trail was alongside, or was in, the river that flowed through the canyon. The high point of the run is getting to the old dam that was the head of the irrigation channel to carry water to fields outside the canyon. Along the way you’ll see some mysterious doors I presume were for maintenance of the tunnels. I would avoid this run if there is any sign of rain since it could get very dicey quick.
The Waimea Canyon Lookout is less than an hour drive from any town along the coast between Waimea and Koloa along Highway 50. If you start early, you can be up and down the mountain, get in a decent run and then still get in an early afternoon swim.