The Grand Canyon, one of the most majestic portraits of nature I've ever seen. Nature in general impresses me, but that place was so vast, and silent at the same time...it was the silence that made me step back and think how amazing it is. Theres this whole huge rift in the earth, and you expect echoes or wildlife sounds, or some sort of background noise of insects or birds, and it's so open that there is nothing for the sound to echo off of so it just sounds silent there. It's really pretty surreal, and amazing. I only had about 3 hours there, but if I ever go back I will plan an entire week to spend there.
Also, the battlefields of Gettysburg. I was only 12 when I visited there, but the earth just felt so somber there...so many lives lost. Even at a young age I felt that the whole place was just filled with sadness.