Erdene Zuu Monastery is the oldest surviving Buddhist monastery in Mongolia, built in 1586 near the ruins of Karakorum. Surrounded by a wall with 108 stupas, it once housed hundreds of temples and thousands of monks. Although it suffered destruction during Stalinist purges in the 1930s, parts of it survived and it now functions as both a museum and an active place of worship. It’s a major cultural and spiritual site in Mongolia.