Combine potatoes, water, and salt in a large pot and place over high heat. Once boiling, reduce heat to maintain a simmer and cook potatoes for about 15 minutes, or until tender when sliding a fork into the center. Drain and cool for at least 30 minutes in the refrigerator.
When potatoes are cool, mix with dressing, arugula, and feta until all ingredients are coated. Plate the potato salad and garnish with toasted pine nuts.
This dish is a great make-ahead items for parties or picnics, simply add the dressing when ready to eat.
Feel free to add other fun ingredients like kalamata olives, fresh basil or red onions for unique flavor combinations.