Central Rail Line (Polish: Centralna Magistrala Kolejowa, CMK, also known in Poland as the Rail Line No. 4, Polish: Linia kolejowa nr 4), completed on December 23, 1977 could have been the first high speed railway line in Europe. Designed for speeds of up to 250 km/h, the line goes from the city of Zawiercie in Zagłębie Dąbrowskie region of southern Poland, to Grodzisk Mazowiecki in the suburbs of Warsaw.