Complex sentence: The Château de Blain or Château de la Groulais, is a mediaeval castle constructed in the 13th century and heavily remodelled in the 16th, located in the "commune" of Blain in the Loire-Atlantique "département" of France.
Split into simpler sentences: The Château de Blain is a mediaeval castle constructed in the 13th century and heavily remodelled in the 16th. It is in the "commune" of Blain in the Loire-Atlantique "département" of France.