On 18 September 2025, workers drilling from opposite ends of the Brenner Base Tunnel met underground — 29.1 kilometres into solid rock, off by just 6 centimetres. The moment marked a new kind of mountain crossing for Europe.
The Alps have always been a problem for European transport. For centuries, the only way through was over — passes at altitude, closed by snow in winter, slow at every season. Railways changed that in the 19th century with tunnels like the Gotthard and the Mont Cenis. But even those bored through the mountain at elevation: trains still climbed steeply to reach the bore, slow and fuel-hungry. The Brenner Base Tunnel is built on a different logic. It goes through at the base.
On 18 September 2025, the pilot bore of the Brenner Base Tunnel achieved its breakthrough — the moment when workers drilling from Austria and Italy met underground. The gap between the two approaching headings, after 29.1 kilometres of boring through the Brenner massif, was 6 centimetres. For a tunnel of this scale, that is essentially perfect.
The numbers behind the bore
When complete, the Brenner Base Tunnel will be the world's longest railway tunnel — 64 kilometres end to end, connecting Innsbruck in Austria to Fortezza in northern Italy. The current record-holder, the Gotthard Base Tunnel in Switzerland (opened 2016), runs 57.1 kilometres. The Brenner will exceed it by nearly 7 kilometres.
The September 2025 breakthrough was the pilot bore — a smaller-diameter exploratory tunnel that precedes the full excavation. The two main running tunnels and a central service tunnel still require completion. Total project cost is estimated at €8.5 billion. The full tunnel is scheduled to open in 2032.
Why base matters
The old Brenner railway, opened in 1867, reaches 1,370 metres above sea level at its summit. Trains climbing that gradient consume more energy, require more powerful locomotives, and move more slowly — particularly freight. The base tunnel enters at 457 metres on the Austrian side and exits at 752 metres in Italy. There is no summit. Trains pass through a gentle grade, almost flat, entirely underground.
The travel time between Innsbruck and Bolzano — a journey that currently takes approximately two hours by rail — will drop to around 50 minutes once the tunnel opens. For the freight market, which currently sees heavy truck traffic over the Brenner Pass highway, the tunnel is designed to shift substantial road freight to rail, reducing both congestion and emissions on one of Europe's busiest alpine crossings.
Drilling through geology
The Brenner massif is not uniform rock. The bore passed through faulted zones, areas of high groundwater pressure, and sections where rock conditions changed without warning. Tunnel Boring Machines were used through competent rock, while drill-and-blast methods handled the harder mixed sections. The 6-centimetre alignment accuracy achieved at breakthrough — across 29.1 kilometres through variable geology — reflects the precision of GPS-guided boring and continuous laser surveying underground.
The September 2025 breakthrough marked the pilot bore only. The full excavation work — widening tunnels, installing rail infrastructure, building the ventilation systems and emergency stops — continues through to the 2032 target.
A century of mountain tunnelling, continued
The Brenner Base Tunnel sits in a tradition stretching back to the Mont Cenis Tunnel (1871), the first major alpine bore. Each generation drove longer, deeper, and faster. The Gotthard Base Tunnel, opened after 17 years of construction in 2016, set the current record and proved that a 57-kilometre bore was operationally manageable. The Brenner extends that precedent by connecting two national rail systems — Austrian Federal Railways and RFI in Italy — through a structure neither country could have built alone.
When trains begin running through the Brenner Base Tunnel in 2032, the Alps will have become, for the first time, something close to flat.
Sources
- Newsweek — Brenner Base Tunnel breakthrough connects Austria and Italy underground
- New Civil Engineer — Brenner Base Tunnel pilot bore breakthrough achieved
- Euronews — Brenner Base Tunnel: Europe's mega-project nears milestone
- Railway Gazette International — Brenner Base Tunnel breakthrough ceremony