Great Sand Dune Lake "Ulaagchin Khar" is located west of the Khangai range, 1980 meters above sea level. It's located 80 kilometers (49.71 miles) Northeast of the Erdenekhairkhan village, in the province of Zavkhan, and 110 kilometers (68.35 miles) from Uliastai city. This turquoise-blue lake offers an astonishing spectacle as it has an incredible natural combination of Gobi and Khangai landscapes. It's surrounded by the sand dunes of "Bor Khyar" that literally dive into its waters. The "Tudevtei" mountains at North, "Burkhantolgoi" and "Burgast" ones at East, "Tovkhosh" ones at the southwest, perfectly complete the landscape. Lake is 48 meters (157.48 feet) deep, it stretches 30 kilometers (18.64 miles) long and 5 to 10 kilometers (3,11 - 6,22 miles) wide.

In the middle of the lake, there are 2 islands called “Small and Big Avgash”. Great Avgash is a quiet sandy and suitable place for the roe-deer to giving birth to the offspring in springs, they inhabit near to the mountain in autumn. The shoreline of the lake is rocky and has a lot of different peninsulas and bays that penetrate into the lake water. On the bottom of the lake, there are sand and mud, and gravel, and some water plants occur in the shallow parts of the lake. The clarity of the lake is 8m/315inches and colors are seen as green and blue emerald. The lake is rich in omul, or white fish, while thirteen endemic bird species come every year including whooper swan, greylag goose, duck, and other mammals such as deer, roe deer, fox, wolf, corsac, manul cat, and marmot are seen near to the lake.