Paris has the densest subway system in the world
Tokyo 500km 2
praris 100km2
The following is a list of the top 10 rail systems, underground subways, and metros that receive the most elevated number of passengers per year in the world:
Moscow Metro 3.2 billion : moscow 9 millions inhabitants
Tokyo Metro 2.7 billion : tokyo 8 millions inhabitants
Seoul 1.6 billion : seoul 10 millions inhabitants
Mexico City Metro 1.3 billion : mexico 8 millions inhabitants
New York City Subway 1.3 billion : new york 8 millions inhabitants
Paris Metro 1.2 billion (metro system only without RER system)
aris 2 millions inhabitants
Osaka Municipal Subway 957 million : osaka 3 millions inhabitants
London Underground 886 million : london 7 millions inhabitants
Hong Kong MTR 798 million : hong kong 6 millions inhabitants
St. Petersburg 784 million : St. Petersburg 4 millions inhabitants
Below is a list of the top 10 rail systems, underground subways and metros that have the biggest number of stations in the world:
New York 468
Paris 297 (metro system only without RER system)
London 275
Tokyo 274 (Tokyo Metro 168, TOEI Subway 106)
Seoul 263
Berlin 254
Munich 229
Madrid 190
Mexico City 175
Moscow 171
top 10 subway systems by length
London 415.0 km (171 km underground)
New York City 368.0 km (219 km underground)
Tokyo 292.3 km (Tokyo Metro 183.2 km, TOEI Subway 109 km)
Seoul 287 km
Moscow 265.2 km
Madrid 226.5 km
Paris 212.5 km
Mexico City 201.7 km
Chicago 173.0 km (the most part is elevated or at grade)
Washington 169.5 km