Hiking Olympic National Park By Erik Molvar Ancient Groves Nature Trail From the Sol Due Hot Springs Road, this 0.5-mile loop passes through the old-growth lowland forest that covers the banks of the Sol Duc River. Most of the oldest trees are Douglas fir, although a few stately Sitka spruce rise through a lower canopy of younger western hemlock. Well-drained glacial terraces cup swales and glades where lady fern and vine maple thrive. Townsend's warblers, dark-eyed juncos, and winter wrens are the most prominent forest inhabitants, while belted kingfishers and water ouzels are commonly spotted along the river.