This past weekend we went to Walker Nature Center in Reston. The craftsman-inspired building opened in 2009 for environmental education. The center sits within 72 wooded acres, and includes trails, a pond, and demonstration gardens.
Inside is a great area for kids that includes a reading, activity, and coloring corner. They also have an aquarium, a snake, a turtle, and a bird-watching corner complete with binoculars.
The center is free and open most days, so it makes for a quick and easy change in scenery for any stir-crazy kids. They also have a multi-purpose room, pavilion, and campfire ring available for rental.