Brenner Base Tunnel ('Galleria di base del Brennero' in Italian) goes under the Alps between Italy and Austria. Once completed, with a length of 55 kilometers, Brenner Base Tunnel (BBT) will be the longest railway tunnel in the World.

BBT will be a main route for the freight trains between the southern Europe and Northern Europe. With BBT, the usual traffic jams caused by trucks will hopefully the the thing of the past.

BBT mainly consists of two tubes running in parallel for 55 km between Innsbruck (in Austria) and Fortezza (in Italy). Each of the tubes with a diameter of 8.1 meters will hold one railway truck. One in each direction. These two tubes will have a separation in the range of 40 and 70 meters between them.

BBT is more than two tubes running 55 kilometers. Actually it is a very complex network of tunnels. To start with, there is a third tunnel running in between the two railway tunnels all the way 55 kilometers. This third tunnel has a smaller diameter (5m) and lies about 12 meters below the bigger two tubes. This third tunnel is called 'exploratory tunnel'. It goes 20 meters ahead of the two main tunnels. Bored by the TBM Günther, the main function of this exploratory tunnel is to collect geological information about the rock formation ahead, so that the larger tunnel boring machines coming behind are operated in more efficient manner knowing what sort of rock lies ahead. Once the BBT goes into operations, the exploratory tunnel will function as a water drainage tunnel.

Alps have been created by colliding African & Eurosian tectonic plates. BBT goes under this massive geological formation:

There is much more than these 3 tunnels in Brenner Base Tunnel. Every 333 meters, there is a connection tube between the two main tubes. And then you have service tunnels, emergency tunnels, all these make BBT a magnificent tunnelling enterprise.

Although the graphics below is intended to give the status of the project in February 2020, it basically shows all the tunnel mesh of this gigantic infrastructure project:

Why Brenner Base Tunnel?

On the map\ Brenner Base Tunnel constitutes a tiny portion of the Trans European Transport Network (so called TEN) but arguably the most important portion of it, especially for the South-North route.

The Trans-European Transport Network (TEN-T) is Europe's 'Belt and Road' project. It is a network of roads, railways, airports and water infrastructure in Europe. It is grand plan which is being implemented piece by piece.

If you need further convincing about the scale of the Brenner Base Tunnel, go ahead, watch this video from youtube by Richard Hammond. Car enthusiasts will recognize him from BBC's Top Gear series. In this video, Richard Hammond goes into the Brenner Base Tunnel and looks around:

https://www.youtube.com/watch?v=Ho3r2vgJnx4

All images are from the 'Media Corner' of BBT SE, with the exception of the video which is from Youtube.