From Beijing stadium (subway station exit C) take bus 407 alight at Jian xiang qiao dong (健翔桥东) bus stop then change to bus 658 to Xi jia huo zi (郗家豁子) which is opposite Bei jiao ( 北郊) bus station.

The ticket from Beijing to Erlian cost 200Y, and the guy told us he usually charges 220Y. The bus was late as it had arrived from somewhere else and we were surprised to see a sleeper bus which means 180 deg flat beds. The walkways were narrow so it might be difficult to pass if you’re carrying backpacks, and the luggage has to be stowed at your feet. Overall the bus ride was comfortable and took 12h to reach the border town of Erlian.
We met an Argentinean girl Paula at the bus station who was also going in the same direction. The three of us shared a cab to the Chinese border control. It is cheaper to hail a city cab from outside Erlian bus station, just ignore the touts and walk outside.

At the border, we met several other foreigners who were also waiting to cross the border because it opens at 8.30am. We manged to get a minivan to transport all of us to the Mongolian side.
After the Chinese customs, we boarded the minivan which drove across to Zamyn-Uud on the Mongolian side. The van did not want to drive us to the Zamyn-Uud train station, but he helped us to get a minibus which transported us and several others.

Since we arrived at 11am and the daily train to Ulanbaatar only leaves at 7.05pm, we got our train tickets (22850T for hard sleeper) and walked around the area. There was nothing much to explore so we had lunch at the restaurant and sat there to chat or play cards for the whole afternoon until they chased us away because the evening crowd had arrived and we were taking up too much space.

The train was comfortable but it was a super long journey of 15h for a little over 700km. They provided free flow of hot water which is good for those with cup noodles and instant beverages. They also provided instant mix coffee and clean sheets for the beds. There were vendors selling dinner and snacks but the prices were slightly more expensive. We finally arrived in UB at 10am on Sunday, wrapping up our 30h border crossing adventure since we started in Beijing.