To a large mixing bowl, add the arugula. Tear the basil and mint (or roughly chop), and add to the bowl.
Pour in the lemon juice and gently toss by hand. Layer half of the arugula and herb mix onto a serving platter or in the bottom of a large salad bowl.
Using a melon baller, scoop small rounds from the melons. Scatter half of the melon balls across the arugula, followed by half of the grapes. Repeat, layering the remaining arugula over the top, followed by the remaining melon and grapes, then dot with the mozzarella.
Top the salad with the chopped pistachios and a garnish of additional basil and mint. Season with salt and black pepper, then drizzle with olive oil and balsamic vinegar. Taste to adjust seasoning and herbs, then dig in!