If you want to make a Denver resident lose his or her constitution, collapse, and make rancorous mutterings, all you have to do is say, "I-70 corridor." The interstate between Summit County and Denver is usually backed up like a toilet full of wigs. Therefore, it doesn't seem to occur to most Denver residents to drive to Frisco for a mountain bike ride. However, the drive is barely over an hour, and the riding in Frisco and Breckenridge is well worth it, and a great mid-summer alternative to Buffalo Creek.
The Peaks Trail is more fun to ride from south to north. You can either park in Frisco and ride the paved bike path to Breckenridge, or simply ride the trail as an out-and-back (do it!).
Park at the Frisco bike park and head west on the bike path. You'll eventually see a brown sign announcing that Rainbow Lake is to your left. Go to there. The climb up to the lake is short, but rocky and a little technical. It's the kind of rocky ascent that requires a lot of power to churn over the rocks (always spaced at odd intervals) but there aren't any huge features that are incredibly difficult to climb.
There are always people taking group photos at Rainbow Lake. If you can ruin more than five group photos without putting a foot down, you win a prize!
There are many unmarked trails leaving Rainbow Lake. Make sure you find the sign for Peaks Trail.
The climb begins here in earnest. It's lengthy but steady, and the pitch is fairly mild. There are a few steeper, rooty sections, but it's a mostly pleasant climb through a forest that's about as lush as forests get in Colorado.
You'll ride alongside a ditch for awhile, and you'll cross a couple of log bridges. At some point, the trail must descend--as it certainly feels like climbing when you're going the other direction--but it never really stops feeling like climbing when you're going this way, either. This last bit is rocky and rooty, and requires maneuvering, horsepower, and luck. So fun!
Eventually you'll pop out in the parking lot at the trail's southern end. There's a condo complex there, and some signage. It'd be hard to miss. Turn around, go 50 feet back into the forest and have your snack where it's pretty.
Some of the aforementioned signage.
After your snack, you'll climb for a couple of miles back through the rocky, rooty section. It's strenuous enough that by the time you cross the long log bridge, you'll want to stick your head in the creek.
Not long after you cross the creek you'll begin a long, ripping descent. Root drops, jumps, shred turns! Yes!
At the bottom, you'll have an easy pedal back along the bike path to your car. Now you can play at the bike park. Check the internet; if there's a ton of traffic, play at the bike park for a long time. Eat tacos. If traffic is still bad, just stay in Frisco. Forever.