http://news.dayoo.com/guangdong/201610/30/139996_50366218.htm
Shenzhen Metro now has 8 lines which amounts nearly 286km. It's the 4th largest metro network in Mainland China.
And the total length of the metro system exceeded that of the neighboring world city, Hong Kong.
When we consider that Shenzhen was just a small city which population was less than a million, it's astonishing speed of growing.
