From Fairfax County Park Authority:

On Saturday, November 19, 2011, from 6 to 8 p.m., visitors will gaze through a 10-inch telescope at our solar system’s largest planet, Jupiter, during Riverbend Park’s annual Night Sky Festival. Due to the dark, moonless night, Jupiter’s colors and banding should be visible. The planet’s four Galilean moons (Ganymede, Io, Europa, Callisto) are also expected to be seen. The festival occurs near the peak of the Leonid meteor shower and, although rare, participants may occasionally see shooting stars while listening to stories by a warm campfire.

From Fairfax County:

If you’ve been postponing that overnight trip to the woods because gas is so expensive or your schedule is full, consider an adventure closer to home. Families can enjoy a blazing campfire and night hike at Riverbend Park located in Great Falls, VA. Get away from it all right here with the Fairfax County Park Authority!

From Fairfax County:

From 9 to 11:30 a.m. on Saturday, April 9, 2011 help clean up streams in your community's parks during the 23rd Annual Potomac Watershed Cleanup Day. Individuals, students, families, scouts and other groups can help remove tires, bed springs, bottles, cans, and other myriad debris from local waterways. Boots with sturdy soles are recommended. Wear old clothes and bring gloves. Trash bags and appreciation will be provided.

To reserve a section of the watershed, please contact a park from the list below.