Complex sentence: Northernhay Gardens are located in Exeter, Devon on the northern side of Rougemont Castle, is the oldest public open space in England, being originally laid out in 1612 as a pleasure walk for Exeter residents.
Split into simpler sentences: Northernhay Gardens are located in Exeter, Devon on the northern side of Rougemont Castle. They are the oldest public open space in England, being originally laid out in 1612 as a pleasure walk for Exeter residents.