Complex sentence: One of his most famous painting is "Geschiedenis van het gebeente van Johannes de Doper" or "The Legend of the Relics of St. John the Baptist" was part of a larger triptych for an altar of the Knights of St. John at Haarlem.
Split into simpler sentences: One of his most famous paintings is "Geschiedenis van het gebeente van Johannes de Doper", or, "The Legend of the Relics of St. John the Baptist". It was part of a larger triptych for an altar of the Knights of St. John at Haarlem.