Seoul and Barcelona metro operators sign co-operation agreement
http://www.metro-report.com/news/metro/single-view/view/seoul-and-barcelona-metro-operators-sign-co-operation-agreement.html
What's the similarity between Seoul Metro and Barcelona?
Though all of the rails in Seoul Metro are 1435mm gauge, railways in Barcelona Metro ranges from 1000mm to 1674mm.
The total length of the system in Barcelona is 123.7 km, while that in Seoul is longer than 1000 km.
And, manufacturers of the rolling stocks do not coincide with each other.
Then, it's mysterious that these far two cities tried to cooperate.