Amasa Back is a 8.7 mile loop trail located near Green River, Utah that features beautiful wild flowers and is rated as difficult. The trail offers a number of activity options and is accessible year-round.
This is a steep technical ascent to one of the best view in Moab in my honest opinion. The trail leads up and around the side of a mesa where you look over into Jackson Hole which is basically a giant butte surrounded by a canyon forming a giant circle. From here you can continue to Pothole arch which is well worth the ride and on the way back you can ride an extremely technical route Rockstacker back.
Lot more info here: http://adventeurs.com/captain-ahab-cliffhanger-pothole-arch-mtbing-in-moab-ut/
This trail is my favorite in Moab. The way up is basically one huge technical climb. I'm primarily a downhiller and walked lots of the way but if you are into cross country this climb will be a very fun, and a very challenging test.
Once at the top, the views are simply spectacular. You have a 360 degree mountain view that is a great opportunity for a good picture.
Coming down is a technical downhill. You can make it down very quickly but if your not a downhiller everything is easy to go slow or even walk over.
This trail is a "Locals" favorite, and can be VERY busy. Amasa back is a P2P [point to point] trail of about 10 miles. Vertical climb is 1050 feet.
This trail is both technically and physically demanding but the reward of some stunning scenery is well worth it.
If it was not for the crowds, this could well be Moabs best ride, if possible do this trail on a weekday.