I - Across countries and cities:

• The number of countries with metro systems: 60

• The number of systems currently in operetion: 185

• The number of systems currently under construction: 29

• The northernmost metro system: Helsinki (Finland)

• The southernmost metro system: Buenos Aires (Argentina)

II - By total length of lines:

• The largest metro system by length of lines (613,2 km): Shanghai (China)

• The smallest metro system by length of lines (only 5,9 km): Lausanne (Switzerland)

• The total length of subway lines: 14281 km (on 10.09.2019)

III - By number of stations:

• The largest Metro by number of stations (424 in total) New-York / Seoul (USA / South Korea)

• The smallest Metro by number of stations (only 4 stations): Ahmedabad (India)

• The total number of stations on existing subways 11874 (on 10.09.2019)

IV - Year of opening date:

• The oldest metro: London (UK);

• The youngest metro: Hohhot (China) - on 29.12.2019.

V - Interconnected/Coupled metro systems:

• INDIA: Delhi - Noida - Gurgaon;

• SOUTH KOREA: Seoul - Incheon - Uijeongbu;

• CHINA: Guangzhou - Guangfo;

• CHINA/TAIWAN: Taipei - Tayuan;

• USA: New York - Newark;

• VENEZUELA: Caracas - Los Teques;

• TURKEY: Istanbul - Gebze (under construction).

VI - Top "12" largest Metro systems:

• Shanghai (China);

• Beijing (China);

• Seoul (South Korea);

• New York (USA);

• London (UK);

• Moscow (Russia);

• Tokyo (Japan);

• Delhi (India).

• Chongqing (China);

• Chengdu (China);

• Wuhan (China);

• Madrid (Spain);