most extensive metro systems in the world

The second city in China to open a metro system after Beijing, Tianjin has 80 miles of track that service 76 stations.

The subway system of Busan in South Korea, this underground network has 128 stations along 81 miles of track.

An integral part of the extensive mass transit system of Greater Osaka, the Osaka Municipal Subway runs for 86 miles and stops at 101 stations.

This rail network in the German city of Hamburg makes stops at 68 stations along 86 miles of track.

Spanning the entire city-state of Singapore, the MRT services 89 stations along its 91 miles of track.

Serving the San Francisco metropolitan area, BART operates five lines on 104 miles of track with 44 stations.

Commonly referred to as the Metrorail, Washingtons rapid transit system is the second busiest in the United States after the New York Subway.

Short for elevated, the L is the rapid transit system serving the city of Chicago and its surrounding suburbs. Its the second longest rapid transit system in the United States after New York and third busiest (after New York and Washington D.C.)

The official rapid transit railway system in Hong Kong, MTR covers 108 miles of track and stops at 82 stations.

This large suburban network crosses the city of Valencia, with all trains continuing out to far-flung suburbs. It has 109 miles of track and 169 stations.