Along the Kolob Terrace Road between the ever-so-popular Left Fork Trailhead and the Right Fork Trailhead is the overlooked and unloved Grapevine Trailhead. With so many other more interesting hikes nearby (like the famous Subway route), many will wonder what exactly does this trailhead lead to? After years of ignoring it as I drove past it to do more exciting things, I finally took a day to investigate. The Grapevine Trail is a short route that descends through the lava cliffs and provides fairly easy access to the bottom of the Left Fork, roughly 1.3 miles downstream of where the Subway route accesses the water. Grapevine Trail is not really an alternate start to the Left Fork (Subway) or the Right Fork routes; it's just a short hike down to a pleasant watering hole.
A hike along the Grapevine Trail (also called "Grapevine Spring" in some of the old NPS literature) may take 30-45 minutes (one way) to get to the water. From the trailhead, hike east along the official trail of use and within minutes, you will be standing at the edge of the lava flow hill looking down into the Left Fork. An old sign tells you that you are entering Zion wilderness. Now the route gets a bit more interesting. Follow the trail as it zigzags its way down through the big lava rocks to descend to the bottom of the hill. Since this trail doesn't get much action, it can be faint at times and there are a few steep sections, but there is nothing too treacherous. Prickly-pear cacti are often growing right in the middle of the trail.
Soon enough, you'll make your way to the bottom of the lava flow hill at a flat bench just above the river. Here the trail of use hits a junction where you can head either north or south on even more faint trails of use. Pick your poison and soon enough, you'll be sitting along the banks of the Left Fork. Enjoy the babbling water, take a dip, and return the way you came. Allow 30-60 minutes for the return hike. (The trailhead is roughly 350 feet higher than the river, so it will take a bit more work to get back up.)
This isn't really a destination hike that I would recommend to the general public, but it's a not-too-difficult route to a fairly pleasant watering hole. (On a hot summer day, the water is perfect!) This route isn't very photogenic, but the day we hiked (early summer), we saw a lot of wildflowers, a collared lizard, and many canyon treefrogs along the river.