Its surprising to think you can live somewhere for years and years and not realize how close you are to a place as beautiful as Great Falls. The park had a $10 fee per vehicle, but it was well worth the cost. Just a short walk from the parking lot is the overlook, which has amazing views of the river, and then you can take your pick of multiple hiking trails along the river.
It gets very crowded in the afternoons, but at 9am in the summer it was practically empty. As fall is beginning, I'd say its a great time to go. Make sure to bring everything you need for hiking if you decide to do more than just the path to the overlook. The Billy Goat trail is the most rigorous, and the longest, and much of the trail is covered with rocks so good hiking shoes are important.
I'm hoping to try out the Virginia side soon, but I've heard from friends that it isn't as well up kept. I'll let you know how it goes!
This is a great day hike right outside Haymarket. The longest trail is about a 3 mile loop, the problem, however, was that it was supposed to come to a peak, but it never did. We noticed a trail was closed towards the middle, so we figured maybe the peak area had been temporarily restricted for some reason. It was a bit of a disappointment to not get to an overlook point, but the hike itself was very scenic and even passed some historic sites. The incline was rarely challenging and the path changed from narrow dirt paths between beautiful overgrown plants to stone and pebble walkways beside the river with no green in sight. We took the green trail, the longest route, and it took less than 3 hours. We noticed only a few other people on the trail, so it wasn't overcrowded at all. Very kid friendly because its relatively flat and there and multiple shorter options. We saw a lot of dogs also, but the trail prohibits them, however it seems like they wouldn't notice things like that. Also prohibited is camping, which wouldn't be necessary on such a short hike. All in all, it was a very easy and quick day hike.