This ravine is a fine example of what’s called a glacial outwash basin (a remnant from the last ice age). The hollow was the first piece of property purchased in the island’s 50-year tradition of land conservation, an effort that has succeeded in saving half the island’s land from development. From the West Side Road trailhead, you can descend along winding pathways to the base of the hollow or hike to the south coast of the island to lie on the beach, below cliffs of clay. It’s a half mile hike to the beach. You can also choose to take a longer hike to nearby Fresh Pond.