Summer is already on everyone's mind—especially on Pinterest. Since the beginning of 2016, Pinterest has tracked the most-pinned summer travel destinations, and this year it looks like Pinners are itching to skip town and go off the grid. Topping the list are some of the world's most beautiful waterfalls, national parks, and crystal-clear swimming holes including places as close as the Grand Canyon and as far-flung as New Zealand. The only question is, which place will you pick for your…