Citybanan is the working name for a 6 km railway tunnel under Stockholm. As can be seen Stockholm is surrounded by lots of water and there has been a major bottleneck in railway traffic from the south coming into the central station in Stockholm. The metro has its own rail system but the commuter trains, cargo and the national rail all compete for the same tracks. All trains going from southern Sweden up north also need to go through Stockholm. The tracks only have a capacity of 28 trains per hour and a total of 24 trains run per hour at peak time.
The Citybanan will be a two-track system for the commuter trains. Two new downtown stations are being built at the same time and the capacity will rise to 48 trains per hour. The maximum depth is 40 metres, with the tunnels partly running under the metro system. This produces an incline of up to 3% A rescue tunnel parallels the running tracks. The tunnels beneath land are drilled through the granite bedrock. A submerged tunnel has started to be made in the water close to Gamla Stan.
The underground workings where the tunneled section will connect with the submerged tunnel were open for public viewiung on several occasions. A large group of Sub Brit members joined a tour in May 2011 for an unforgettable experience.