In Beijing, the subway is the fastest, most affordable, and eco-friendly way to travel. In this episode, Professor Mahoney visits Zhengxin Garden Community, located near Songjiazhuang Station, a key hub where three subway lines intersect.

Although Zhengxin Garden Community is close to Songjiazhuang Station, residents must walk nearly a kilometer to access it, because a wall between Zhengxin Garden Community and Hongshi Homeland Community block the former's access to the Station.

Residents of Zhengxin Garden Community propose opening a gate in the wall to ease travel, but residents of Hongshi Homeland Community disagree, citing concerns over losing limited parking space.

Wall keeper versus path seeker. Who will win? Are there other solutions? Click the video to find these answers.