Natural Tunnel State Park features a 100-foot-wide, 850-foot-long natural limestone tunnel carved by Stock Creek over millions of years through a solid mountain ridge — often called the 'Eighth Wonder of the World.' A chairlift descends to the tunnel floor where an active railroad track creates a surreal juxtaposition of natural geology and industrial heritage. The surrounding park offers a swimming pool, campground, and hiking trails. A genuinely spectacular natural feature within easy day-trip range of the Tri-Cities.