Protected within the Khorgo-Terkhiin Tsagaan Nuur National Park, this scenic freshwater lake is around 16km long, east to west, and around 4km to 6km wide, north to south. It takes around two hours to walk from Tariat to the northeast corner of the lake (6km). Here you'll find the largest concentration of ger camps, plus some shops selling drinks, snacks and cooking provisions. It's just about perfect for camping (though there are a few flies in summer).
According to legend, this lake was formed when an elderly couple forgot to cap a well after fetching water. The valley was flooded until a local hero shot a nearby mountain top with his arrow; the shorn top covered the well and became an island in the lake (Noriin Dund Tolgoi). Another, more plausible, theory is that it was formed by lava flows from a volcanic eruption many millennia ago.