Complex sentence: From the city, the road goes northeast and then starts paralleling the Snake River, the border between Washington and Idaho, and becomes Riverside Drive on the opposite side of the river from Hells Gate State Park, located in Idaho.
Split into simpler sentences: From the city, the road goes northeast and then starts paralleling the Snake River, the border between Washington and Idaho, and becomes Riverside Drive. The highway, which is on the opposite side of the river from Hells Gate State Park in Idaho.