Granite Falls Hot Springs is located near Jackson, WY and features hot springs. The trail is primarily used for hiking.
The trailhead to the hot spings is actually about 30-40 min drive outside of Jackson. I rented a fat tire bike and did the round trip from the trailhead to the springs (20-22 miles with time off the trail) in Jan. I suppose this could be a hiking trail in summer, but due to the distance, would recommend bikng it. In the winter, the trail is predominantly used for dogsleds and snowmobiles.
As this was my first fat tire bike ride, I wasn't sure of the logisitics. If its snowed recently, as it had prior to my ride, the bike wi will not grip the trail and one will have 22 miles of hellish fishtailing and skidding. If you can be assured of a packed base, then go for it, or go when there is not snow on the ground. There are outfitters in Jackson who rent bikes, and who will take you on a guided snowmobile or dogsled ride.
Aside from the logistics of getting there, the springs are a warm respite from the cold, have primitive pit toilets and changing rooms, but are not crowded because of being off the beaten path. They have water and a few snacks for sale (cash). The facility closes at 5 PM in the winter, and I saw a campground on the trail about a mile back, but did not see anyone winter camping there.
Scenery along the way is beautiful, quiet, and worth it, but again, if recent snow, there can be avalanches onto the trail (there was one the the week after my ride which took out two snomobilers...who made it out OK).
I loved the trip, but would not ride a fat tire bike there again unless I the snow was was not fresh.
If you are travelling from out of town, keep in mind the altitude is a contender, as is the dry air.