Question: In what half of the 16th century was the castle that overlooks the river that flows between Glenbuck and Crossford built? built?
Sentence (from "River Nethan"): The area of woodland surrounding the River Nethan at Crossford and Auchenheath has been declared a site of special scientific interest and forms a part of the Clyde Valley Woodlands National Nature Reserve as Nethan Gorge.
Relevant evidence: No