Locals, and some historians, claim that Avarga, not Karakorum, was the first capital of the Mongol empire. The ancient tent-city was located in the modern-day Delgerkhan sum (district), on a 20km-wide plain, Khödöö Aral (Countryside Island), so named because it is encircled by the Kherlen and Tsenkheriin Gols.
As in days of old, the town is a huge ger encampment bisected by several streets, with a few incongruous-looking wooden houses sticking up here and there.
The main sight is the Avarga Toson Nuur, the lake that flanks Delgerkhaan, fenced off to keep out livestock and campers. Its water and mud are reputed to have medicinal properties, and it's the one place in eastern Mongolia where you'll find locals bathing, strolling and jogging around the lake. On one bank stands an impressive ovoo; on the other, a shrine.
Thirteen kilometres south of Delgerkhaan village stands the Chinggis obelisk, featuring the visage of the khaan on one side. It was erected in 1990 to commemorate the 750th anniversary of the writing of The Secret History of the Mongols. The symbols on the side of the obelisk are the brands used by about 300 different clans in the area for marking livestock.
One kilometre east of the statue is the Avarga Toson Mineral Spring, from which Ögedei Khaan drank and was cured of a serious stomach ailment. You can fill your water bottles with the delicious, naturally slightly salty and carbonated spring water at a pump house near the site for T100 a bottle.
Take the paved road between Ulaanbaatar and Chinggis Khot to Jargaltkhaan, then travel 42km southwest on a decent dirt road to Delgerkhaan.