The Trans-Mongolian Railway is the main rail link between Mongolia and its neighbors. It begins at the Trans-Siberian Railway in Russia at the town of Ulan-Ude, crosses into Mongolia, runs through Ulaanbaatar, then passes into China at Erenhot where it joins the Chinese railway system. A separate railroad link connects the eastern city of Choibalsan with the Trans-Siberian Railway. However, that link is closed to passengers after the Mongolian town of Chuluunkhoroot.