Trans Siberian Railways is a Rail Line goes to Moscow, Russia to Vladivostok, Russia. That is about 9,282 km. It is a 6 Day Journey, 60 Stops, and Several Time Zones.

The Trans Mongolia Railway is a Rail that goes to Moscow, Russia to Beijing, China. That is about 7,826 km. It is a 5.5 Day Journey, 30+ Stops, and 127 Hours.

 Both these Lines can be tie in with each other. Tran Siberian Railway- Moscow to Vladivostok-Trans Mongolian Railway- Moscow to Beijing.

You can take The Trans Siberian Railway to Mongolia or Beijing, China and Back.

Info- http://traintravelexpert.com.