Complex sentence: The Prix Niel is a Group 2 flat horse race in France for three-year-old thoroughbreds (excluding geldings) run over a distance of 2,400 metres (approximately 1 mile 4 furlongs) at Longchamp Racecourse in September.
Split into simpler sentences: The Prix Niel is a Group 2 flat horse race in France for three-year-old thoroughbreds (excluding geldings). It is run over a distance of 2,400 metres (approximately 1 mile 4 furlongs) at Longchamp Racecourse in September.