Potomac Heritage Trail

The scenery along this trail is amazing. You feel like you are in a completely different place, transported farther away from the city than you really are. Almost completely shaded, the trail is a nice respite from the heat in summer, with beautiful views of the river year round.
The trail is lightly used, which can be a good or a bad thing. It means that it will be peaceful and less crowded than other hiking trails in the area, so it is good for trail running. But it also means that you can feel isolated. I’ll admit that I have run the trail alone, but I immediately realized it was a bad idea. Now I prefer to bring company.
The trail does get a little rocky at parts, so if you’re trying to run, expect some slower going.
The only downside to this trail is that the section that is closest to the city (starting at Roosevelt Island) is littered with trash. I have never seen so much litter in a park in America before.

The Potomac River is beautiful and a national treasure. The Park Service does a great job of preserving the beauty for the visitors. Rafting, tubing, kayaking, canoeing, boating, jet skis, wake boards, and water skiing are all popular on different sections!

OK, I haven’t hiked the entire trail to PA. I’ve only hiked from Roosevelt Island to 495 bridge, not a short hike nonetheless.
I have seen:
perhaps the biggest trees in VA
lots of junk [makes me want to clean up water ways and stop people from polluting]
the three sisters rocks
anchored boats in the summer
folks biking on the canal trail across the river
Georgetown U.
I have fished for spawning fish with my Dad as a kid, and caught quite a few.
I have found some of the most tranquil space inside the Beltway possible. You can hike nearly the whole trail on a weekend without seeing other people.
Note: if there has been a lot of rain recently, be wary. Trees can be down across the trail and high water in the Potomac can be very treacherous.