Seoul originally had just one subway line, 7.8 kilometers in length, constructed in 1971. In order to meet the demand of the Olympic Games, three new lines were constructed in less than seven years.
漢城原本只有一條建於一九七一年、長僅七．八公里的地下鐵；為了配合奧運，又在七年時間裡增建了三條。