In the mid-13th century, Karakorum was a happening place. Chinggis Khaan established a supply base here and his son Ögedei ordered the construction of a proper capital, a decree that attracted traders, dignitaries and skilled workers from across Asia and even Europe.
The good times lasted around 40 years until Kublai moved the capital to Khanbalik (later called Bĕijīng), a decision that still incites resentment among some Mongolians. Following the move to Bĕijīng and the subsequent collapse of the Mongol empire, Karakorum was abandoned and then destroyed by vengeful Manchurian soldiers in 1388.
Whatever was left of Karakorum was used to help build, in the 16th century, the enormous monastery, Erdene Zuu Khiid, which itself was badly damaged during the Stalinist purges.
The rather nondescript Soviet-built town of Kharkhorin was built a couple of kilometres away from Erdene Zuu Khiid, and there is little of interest in the town itself (don't come expecting the glories of the Middle Ages!). But the remains of the monastery and a very impressive new museum – both walking distance from town – pull in punters by the busload, while the town's strong selection of ger camps and guest-ger accommodation, plus some decent horse-trekking outfits, ensure plenty of people linger for a while.
Kharkhorin is also within easy striking distance of a number of worthwhile sights – the stunning lakes of Naiman Nuur, Orkhon Khürkhree waterfall, the secluded hilltop monastery, Tövkhön Khiid, the sand dunes known as Mongol Els, and the magnificently stark rocky nature reserve, Khögnö Khan Uul – making this the best place to base yourself for a tour of Övörkhangai aimag.