I'm going on a solo vacation soon, ideas?

I’m getting about ten days off from work, ideally I want a solitary camera and a notebook adventure. I have a car and would be willing to drive about 100 miles any direction from the DC Metro area.

I’d like to see some beauty either natural or man-made. I know this is a bit vague but I’m hoping someone knows some quirky or hidden things to do. And don’t say Skyline Drive, that’s already on my list. :)

Cost is important my budget at maximum outside of gas is twenty bucks a day.