The first section of the M1 line was opened on January 28, 1988. It is 6.5 km long. and 5 stations that connect Slivnitsa Blvd. through Lyulin Quarter with K. Velichkov Blvd.
In the western part, the M4 line connects to the 2nd metro diameter at Obelya station.
In the eastern part, the 1st metrodiameter is divided into 2 rays
- northern (to Druzhba district and Sofia Airport, opened on April 2, 2015)
- southern (to Mladost district and Sofia Business Park, opened on May 8, 2015).
Line M1 (red) - stations:
section Slivnitsa - Mladost I is shared with line M4 - red (Slivnitsa - Lyulin - Zapaden Park - Vardar - K. Velichkov - Opalchenska (at the intersection of Todor Aleksandrov Blvd. and Opalchenska St.)
- Serdika (at the intersection of Todor Alexandrov Blvd. and Knyaginya Maria Luiza Blvd., connected to Serdika II station and lines M2 and M4)
- SU "St. Kliment Ohridski" (connected to Orlov Most station and lines M3 and M4)
- Stadium 'Vasil Levski
- Joliot Curie (near South Bus Station)
- G.M. Dimitrov - Musagenitsa - Mladost I)
- Alexander Malinov
- Academic Alexander Teodorov-Balan
- Business Park (next to Business Park Sofia in Mladost IV quarter);
Line M4 (yellow) - stations
- Obelya (common station with line M2 - blue)- Modern suburb (under construction - near the Obelya depot, lines M2 and M4 will split at this station) - section Slivnitsa - Mladost I is common with line M1 - red (Slivnitsa - Lyulin - Western Park - Vardar - K. Velichkov - Opalchenska - Serdika (at the intersection of Todor Aleksandrov Blvd. and Knyaginya Maria Luiza Blvd., connected to Serdika II station and lines M2 and M1)
- SU "St. Kliment Ohridski" (connected to Orlov Most station and lines M3 and M1)
- Vasil Levski Stadium
- Joliot Curie (near South Bus Station)
- G.M. Dimitrov
- Mladost I
- Mladost III
- Inter Expo Center-Tsarigradsko shose
- Iskar road
- Sofia's Holy Forest
- Sofia Airport (departure exit at Terminal 2 of Sofia Airport);
On August 26, 2020 after the opening of the 3rd metro diameter, the lines M2 (blue) from Obelya to Vitosha and M4 (yellow) - from Obelya to Sofia Airport are separated.
Construction began in December 2008, and the line was put into operation on August 31, 2012.
Two of the stations on the M2 line (NDK and European Union) and the tunnels connecting them were built during the construction of the NDK in 1981.
All metro stations have a platform length of 104 meters (except for the above 2, whose platforms are of standard dimensions).
During the construction of the Serdika II station at TSUM in the center of Sofia, archaeological finds were discovered, part of ancient Serdika.
For their storage, some changes are required in the initial project - the station is built underground and the construction of an underground parking lot is omitted.
Line M2 (blue) - stations:
- Obelya (common station with line M4 - yellow)
- Modern suburb (under construction - near Obelya depot, lines M2 and M4 will split at this station)
- Lomsko road
- White Danube
- Khan Kubrat
- Knyaginya Maria Louisa
- Central Railway Station (in front of Sofia Central Station and Sofia Central Bus Station)
- Lion's Bridge
- Serdika II (on Knyaginya Maria Luiza Blvd., in front of Central halls - connected to Serdika station and lines M1 and M4)
- NDK (connected to NDK II station and line M3 - green)
- European Union
- James Boucher
- Vitosha (on Cherni Vrah Blvd., near Paradise Center in Hladilnika district);
According to the original design, it was supposed to be built as a surface light metro with an underground part only in the city centre, but this was later changed and it is being built as a classic metro with separate surface sections. Construction begаn in the early 2016. It is planned to have 15 stations on the M3 main line and 6 stations on the Tsarigradsko shose - Slatina branch, of which 2 will be Transfer stations with the other operating lines.
The first section (Krasno selo - Hadji Dimitar) will be put into operation on August 26, 2020. Currently, 12 stations of the M3 main line are functioning, and in 2025 the completion of the remaining 3 stations in the Levski district are expected.
All stations of the 3rd metro diameter have automatic platform safety doors. The trains on the M3 line are overhead-powered (pantograph).
Line M3 (green) - stations
--Vladimir Vazov, Trakia and Georgi Asparuhov Stadium (under construction)
- Hadji Dimitar (next to Poduene Bus Station)
- Orlov Bridge (connected to "St. Kliment Ohridski" public transport station and lines M1 and M4)
- St. Partriarch Euthymius
- NDK II (connected to station NDK line M2 - blue)
- Medical University
- Krasno Selo
- Ovcha Kupel
- Moesia - NBU
- Ovcha KupelII
- Gorna Banya
There are plans to expand the Sofia Metro.
The construction of 4 new sections and 15 new metro stations is planned:
- the section from Lyulin to the ring road and Bozhurishte - with a length of 1.5 km. and 2 new stations; It is planned as an extension of line M1 (red), which will serve Lyulin district.
- a section from Business Park Sofia to the lift in Simeonovo - length 1.7 km. and 2 new stations; It is planned as an extension of line M1 (red), which will serve Mladost IV district.
- a section from Cherni Vrah to Studentski Grad - with a length of 4 km. and 4 new stations; The route is planned as an extension of line M2 (blue) to connect the districts of Lozenets and Ctudentski Grad.
- the section between Tsarigradsko shose and the Military Academy - with a length of 6.1 km. and 7 new stations; This is the longest extension. It is planned as a branch of the M3 line (green), connecting the G.S. Rakovski Military Academy, Geo Milev and Slatina neighbourhoods with Tsarigradsko Shosse to Polygona and The Mall (Sofia).