This is a network of trails on the far SE end of the Bogd Uul range. There are around 40 miles of trail here in an area of about 75 sq km (29 sq mi, 18,700 acres, 8500 hectares). Most all of it is on the north side of the mountain, and much of it forested with rock outcrops scattered throughout. Very beautiful. There is more trail on the south side of the mountain, but I am limiting this description to the north side only. The southern trails are much more barren for the most part. If you added in the south side of the mountain, the mileage would increase substantially.
I have only ridden a small portion of the trails here thus far, but what I have ridden is REALLY nice. The climbs are very nice -- long but not too steep with some challenging spots and hike-a-bike sections here and there. The DHs are a great mix of slow tech, fast tech and all out rippin' fast. There is a good mix of singletrack and double track. The double track is not double wide, but two narrow singletrack side by side. Most of the trails were formed by vehicles, but receive so little use that the track often reduces to narrow singletrack. The surface is a mix of hardback, organic dirt and grass/needle. Five stars so far for the riding, scenery and pristine nature.