To get there by car, you take 123 south from Fairfax for about 5-10 miles, or north from I-95 for about a mile. Along this stretch, 123 gets as wide as about 8 lanes, including a wide, brand new bridge across the Occoquan River.
Getting there by bike is much the same - except that you're taking the bike trail along 123, rather than riding on the highway. With one exception.
As you approach the large bridge across the river from the north, you can go down a side road through the woods. It winds around briefly, passing a few houses before coming to an end. At the end of the road is a narrow wooden pedestrian bridge across the river. If you take this route, you get transported back in time, to a place where people wave to you as you pass them by, where the streets are virtually empty of cars, where you can sit back and relax on the front porch with a glass of iced tea, or browse stores ranging from antiques to scuba. It's a strange little pedestrian bridge, and it's not until you get to the other side of town and come back up to the highway that you realize that you didn't actually get transported anywhere at all, you simply found a little pocket of tranquility, right around the corner from home.
It's the pedestrian bridge, I think, that gets your mind and spirit prepared for the journey.
Route Map w/ placemark for the bridge