The cities of Beijing and Buenos Aires are almost antipodes, i.e. they are situated almost opposite of each other on the globe.
An interesting attribute of this is that travelling between the two cities can be done through any point of earth and the trip will still be roughly the same distance. This D3 visualization demonstrates this principle: drag the map around to change perspective, click the map to set a "midpoint" to travel through.
IIRC this is in a theme in Wong Kar-Wai's movie Happy Together.