As befitting the town where a marathon is one of the year’s most anticipated events, Boston  is crazy about running. Numerous runners’ shops and paths exist to accommodate them. Biking is another story. A few years back, Boston was declared the worst city in the country for biking by Bicycling magazine, and despite some stabs at creating a more cohesive network of bike paths, it has yet to live down the reputation.
Sailboats spice up the view along the Charles River Esplanade (website ), the park of choice for runners, bikers, and inline skaters. A long strip of green along both sides of the river, the park runs 17 miles in a loop from the Charles River Dam to Watertown.
More out of the way, but less traveled, is the Southwest Corridor (website ), a five-mile bicycling and running path that starts in the South End . After crossing Massachusetts Avenue, the path provides a mostly uninterrupted stretch of parkland all the way down to Forest Hills and the Arnold Arboretum .
Landscape designer Frederick Law Olmstead envisioned an “Emerald Necklace” (www.emeraldnecklace.org ) of parks that would encircle Boston , beginning at the Back Bay Fens and including the Arnold Arboretum and Franklin Park. The bulk of the necklace is still intact, especially along the Fens, where running paths trace leafy brooks and brackish fens that seem like they have left the city far behind.
For more hard-core cyclists, the Minuteman Bikeway (www.minutemanbikeway.org ) offers 11 miles of graded terrain along an old rail bed, beginning behind Davis Square in Somerville , and running all the way out to the suburb of Bedford, passing historic Arlington and Lexington  along the way. If you start early enough, you can stop to see the Revolutionary War sights and still be back in plenty of time for dinner.