It can be done!
To be completely honest, I enjoy having all the hills around here. Because the moderate, rolling hills are so ubiquitous, getting hill training in is really easy, and I know I've definitely benefited from having them in the vast majority of my short-to-medium easy/moderate runs. I wouldn't live somewhere flat for all the world! On the other hand, I don't really want to run hills every single day of my life, so having a few flat loops of various sizes in my back pocket is key.
Often when I want to do a longer, relatively flat run, I head for Golden Gate Park. There's a lot to love about running in the Park -- it's reasonably flat in most places (though you can find hills if you want them), scenic, has water fountains along JFK and MLK every few miles, and there are only a few traffic lights. I do enjoy running in the Park and do it a good bit of the time.
On the other hand, it's not super-close to my house. It's close enough that I can run there and back if I want, but not without a) traversing several large hills, or b) tacking on a good 8 miles (counting the return trip) to get there via a route that avoids hills. It's a short drive, so I can always do that if I want, but unless I'm going to the track I try to avoid driving to running because it means extra time spent in the car and also dealing with parking.
And frankly, as much as I enjoy it and appreciate having it nearby, I've looped Golden Gate Park more times than I care to count, and there are days when I just can't face the monotony. So lately I've been experimenting with different routes, partly to break up my routine and partly because I'm always in the market for big, sweeping, medium-to-long flat loops on days when I don't want to run hills or need an easier route. Today I decided I wanted a medium-length easier run, so I decided to see how far I could get without having to run a crazy hill or just turning around and going back the way I came.
Here's my route! (Click to embiggen.)
(In the interest of retaining some semblance of internet privacy, let me just say for the record that the start / finish point on this map is not where or near where I live or where I started, nor do I live on this route anywhere.)
Full disclosure -- it's not completely flat; going south on Divisadero, there is a slightly detectable uphill grade, and maybe a half mile stretch between Oak and Market that does have a few non-insignificant (but quite short) hills. By and large, though, it is AWFULLY damn pancake-y for a loop that large in SF and avoids any truly ridiculous and heart-breaking stretches (looking at you, 17th between Market & Clayton). This will work especially well when I get back to doing *actually* long runs, because it's not too difficult to just tack on a loop through the park. Still working on some way to add in the nice, flat, traffic-light-free stretch of the Embarcadero, but that's a project for another day.