Nanda Parbat is a hidden city nestled high in the mountains of Tibet; it is said to be a place of healing and enlightenment watched over by the goddess-like figure Rama Kushna and her monks. Like Shangri-La, time moves differently in Nanda Parbat. Its visitors are often able to retain their youth many decades after their arrival, and yet can leave Nanda Parbat to find that less time has passed in the outside world. 
- This appears to be part of the plot in "Arrow". Malcolm Merlyn tells his son that after his wife's death, he adventured into Nanda Parbat and had become "enlightened". It is implied that he learned archery and self-defense here.