First, let's get one thing straight: casual travelers won't have time to drive to a gorgeous but far-off trailhead for a workout, so convenience is almost as important as quality. The cities on this list all have long, wide running paths that are close to downtown, offer plenty of scenery, and won’t force you to cross many intersections during an hour-long workout.
The Best Cities For Runners: New York City
Your choices for running routes in New York are limited only by your imagination. In Manhattan, the obvious choice is Central Park: roads there are closed to traffic on mornings, evenings, and weekends, and the perimeter route is more than six miles long. You can also veer off the pavement and take the 1.5-mile loop around the reservoir and through the adjoining dirt bridle paths. Outside of New York's biggest greenspace, my favorite run in the Big Apple is along the Hudson River in Riverside park on the Upper West Side. Outside of Manhattan, check out Prospect Park in Brooklyn, and surprisingly serene Van Cortlandt Park in the Bronx.
You can find a running map of New York here.
The Best Cities For Runners: Minneapolis and St. Paul, Minnesota
Thanks to all of the ponds and lakes within their limits, running in the Twin Cities is more scenic than in just about any other urban area. The route along the Mississippi is a favorite course for runners, as are the paths around Lake Como and Lake Phalen. The Twin Cities Running Club offers a list of routes here.
The Best Cities For Runners: Flagstaff, Arizona
Even setting aside the endless miles of park paths outside the city limits, Flagstaff is the ultimate trail-runner’s haven. Within its confines is a 50-mile urban trail system, half of which is asphalt and half unpaved. It winds along streets and through parks, forests, and neighborhoods, and is accessible from just about anywhere in the city. Find out more here.
The Best Cities For Runners: Washington, DC
A sunrise run around the National Mall in Washington is the ultimate urban workout. Get out that early and you'll have the monuments, and the Smithsonian buildings practically all to yourself. If you're looking for a more serene option, head by the oft-overlooked Rock Creek Park and the tow path on the C&O Canal, which leads all the way to Harper’s Ferry, West Virginia.
The Best Cities For Runners: Portland, Oregon
Thanks to Forest Park, you can go for a distance run in Portland and completely forget you're in a city. The tree-canopied, 5,000-acre park along the Williamette River contains nearly 80 miles of trails, including the popular Leif Erickson Drive. Downtown, runners flock to the paths along the riverfront throughout the day. The Oregon Road Runners Club provides route descriptions of its favorite runs on its website.