The subway in Sofia is the first and only in Bulgaria. It was put into use on January 28, 1998. By 2012 it has a total length of 31 km and 27 stations. In 2013 it is the 34th biggest subway in Europe after Amsterdam and before the subway in Budapest.
The subway is a national object, which means that its construction was financed from the municipal and the national budget, but also from European funds.
Constructionof the busiest line (Ground metrodiameter) and part of the first metro radius begins on March 6, 1978 - from area "Люлин" to "Света Неделя"square with stations"Вардар" and "Люлин".
With the construction of the National Palace of Culture and shaping of the landscape, in the period 1980-1981 has been designed and developed technical infrastructure for the subway. Two stations of the future second diameter and tunnels between them were partially built but station for the third metrodiameter was not started. There were also built stations “НДК” and “Европейски съюз”.
Severe financial crisis of the late 1980s and early 1990s slowedthe construction of the subway down and completion dates were repeatedly postponed. Construction activities resumed in 1995. After 1990,with theurbanization of the square in front of station “Подуяне” several tens of meters of tunnel were built and design for a new subway station is set.
In 2004 begins the preparation, and in 2005 is started the extending of the first metrodiameter through city center from "Света Неделя"square to "Interpred" in area "Изгрев"with a total lenght of 4,8 km and 3 stations. The deadline for completion is the end of 2007. As a main contractor of the project is selected the Japanese firm "Taisei Corporation." In early 2008, the construction period of the tunnel from "Света Неделя"square to the National Stadium "Васил Левски" is extended to 2009. In the early 2006 began to construction of the section from "Interpred" to area "Младост 1" with a total length of 3,2 km and 3 stations.
In July 2007, the Ministry of Transport approves the documentation for selection of the general contractor for the second diameter of the subway station junction "Надежда" - "Кемпински-Зографски". Construction of this section begins in 2008 and ends in 2012.
Construction of the segment from area "Младост" to Sofia Airport with total length of 7,1 km starts as planed in 2009. It’s completed in April 2015 and construction is done in stages:
- I stage - from area "Младост 1" to "Цариградско шосе" with length of 2,14 km. The auction for the section was won by "Метро Младост", which includes two subsidiaries ("PSI" AD, Stara Zagora and "Trace Sofia" JSC, Sofia) of "Trace Group Hold" PLC and "Adval "AD," Stroyinject "AD and three subcontractors. Construction begins on February 15, 2009.
- II stage - from "Цариградско шосе" boulevard to "Искарско шосе" in length: 2870 m and 2 stations.
From "Искарско шосе" to Sofia Airport length: 2090 m, including trestle and 1 station located on it and the last station - above ground, built adjacent to Terminal 2.
OnApril 25, 2013is started the deviationfrom station"Младост 1" to the Business Park(station "Младост 4"). The segmenthas a lengthof2,7 kmanditwill have stations.Deadline: April 2015.