You'll need both a state trails pass ($5 daily/$25 annual) and a state park parking sticker ($8/$11 resident/nonresident daily $11/$30 annual).
The Green Loop
features the same rolling singletrack as the rest of the John Muir system but shaves some mileage and difficulty compared to the all-inclusive Blue Loop
The Bog section features some of the great, forested singletrack characteristics of the John Muir trails, but you'll bypass the longer Squirrel Run section. Next, you reach a couple of small kettle lakes.
After Roller Coaster, you enter Sandy Bottom. This section of the trail is easier except for the presence of some loose, sandy sections. Next, you pass through the beautiful Kissing Meadow and then another sandy section called The Beach.
Following The Beach, the trail twists through a grove of pine trees planted in a perfect grid pattern called the Recovery Zone. You'll want to recover because the most difficult part of the trail, Hell's Kitchen, is coming up. This features its share of rock and root obstacles along with some short, tough climbs and a couple of switchbacks - all the ingredients for a great run.
Once you reach the Cross Roads intersection where the Blue Loop
breaks off towards the Connector - North
trail, the most difficult running is over. You've got about two miles of easy, twisting singletrack back to the parking lot.
You'll want to take some time to explore the other great trails in Kettle Moraine as well.