Tehran's subway system

Updated 4:20 PM ET, Sat February 27, 2016
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The entrance to this Tehran Metro station may be crowded, but it's nothing compared to the car traffic. The Iranian capital's subway system has four lines. Mick Krever/CNN
Tehran's subway system, like much of the city, is covered in art installations. The metro began operating in 1998 with three stations; there are now 70 stations throughout the city. Mick Krever/CNN
The system transports nearly 2 million people per day, according to the Tehran Urban & Suburban Railway Operation Co. Mick Krever/CNN
The Metro is incredibly clean -- no hardened gum, or even dust, to be seen. Mick Krever/CNN
A man sells olives for hungry commuters outside one station. Mick Krever/CNN
A man and his young son watch the tunnel go by. Mick Krever/CNN
Any prepared urban traveler comes with snacks -- in this case, sunflower seeds. Mick Krever/CNN
Not missing an opportunity, the subway's handles double as ad space. Mick Krever/CNN
The subway system has cell phone coverage both in stations and tunnels. Mick Krever/CNN
A man sells balloons -- or tries to sell balloons -- on a train full of mostly uninterested commuters. Mick Krever/CNN
This is what he is up against -- a public service announcement warning commuters against buying from subway salesmen. Mick Krever/CNN
Driving is "a waste of time and a waste of money," says Nima, center; using the Metro is much easier. Mick Krever/CNN