Founding of the monastery of Gradefes Historical milestone · Gradefes, Tierras de León, León Image of Gradefes, not of the place itself. In 1168 Teresa Petri, wife of the knight García Pérez, founded the Cistercian nunnery of Santa María la Real, whose austere and very large church would become the first nunnery in the world to have an ambulatory. 1168 Photo: Simon Burchell (CC BY-SA 4.0) What to see and do in Gradefes