Complex sentence: The road to Bonny Doon from State Route 1 crosses an enclosed, unmarked conveyor belt, which carries limestone from a quarry in the mountains three miles east, to the Cemex cement plant at Davenport.
Split into simpler sentences: The road to Bonny Doon from State Route 1 crosses an enclosed conveyor belt, whose purpose is not obvious. In fact, the conveyor carries limestone from a quarry in the mountains three miles east, to the Cemex cement plant at Davenport.