The Charles River begins somewhere out in the mysterious, unknown lands beyond Route 128, wends its way down between Boston and Cambridge, pauses at a dam to reconsider, and finally empties into Boston Harbor.
Starting in 1893, Boston's Metropolitan District Commission has made a habit of acquiring land along the Charles and turning it into parks. As of AD 2001, they've got a series of connected parks extending seventeen miles1 up the river from the dam at the bottom of the Charles River Basin, just a little ways from the harbor. This is the Charles River Reservation: It begins at the marina by Storrow Drive, within sight of downtown Boston. It ends somewhere in Watertown.
There are paved paths suitable for bicycling and jogging all along the whole series of parks. On the stretch in the city proper, the path is interrupted by three or four bridges. It is exciting to dodge the cars! Farther up, the bridges are more sparse.
The part by Boston, on that side of the river, is called the Esplanade. It's got a bandshell, a hotdog stand, a marina full of sailboats, flocks of geese, and herds of grim fanatics in expensive exercise gear. There are also tourists, pretty girls, children, parents, and a hell of a lot of goose crap. This is where fireworks are launched on Independence Day.
Across the river, along Memorial Drive in Cambridge, is John F. Kennedy Park, which is not nearly so snazzy. Across the river and farther up, in the Brighton stretch, by Soldiers Field Road, there are fine picnic areas with a wide selection of goose crap for the amusement of the discerning scatologist.
All of those areas are mostly grass with a scattering of trees. A few miles farther up the river, in Newton and Watertown, the park on either side of the river is wooded, with paths winding through the trees. Sometimes you can see the river, and sometimes you can't. Sometimes there are long wooden bridges over swampy or uneven ground, with little platforms where you can sit and watch the river and the people. Sometimes the paths skirt suburban back yards or the back lots of small businesses. The river is small, shallow, and idyllic. There are willow trees and there is relative quiet.
In just under an hour, a sedentary computer programmer, past thirty and much the worse for cigarettes, can ride a bicycle from Harvard Square up to the ending of the path in Watertown. There are worse ways to spend an afternoon.
1...or maybe it's eight and a half miles. I'm not quite clear on whether that "seventeen miles" figure is one way or round trip.