It's cheap. It's punctual. And it's green. The subway, despite the crowds during rush hour, has become an indispensible commuting tool for city dwellers. The life of urbanites is increasingly intertwined with rail links, as China will soon surpass other countries in the combined length of its subway systems, which is expected to reach 8,500 kilometers by 2020.

One can find almost anything on subway trains in big Chinese cities -subtle interactions, eccentricity, beauty, sorrow, secrets, kindness, generosity, wacky hairdos...As 2014 comes to an end, we take a look at a few of the many memorable moments underground.

Young men and women dressed in sexy nurse uniforms pose during an AIDS prevention event on World AIDS Day on a subway train in Wuhan city, Hubei province, Dec 1, 2014. [Photo/IC]