Box Tunnel passes through Box Hill on the Great Western Main Line (GWML) between Bath and Chippenham.
The railway tunnel is 1.83 miles (2.95 km) in length, straight, and descends on a 1 in 100 gradient from its eastern end.
The west portal is Grade II* listed and the east portal is Grade II listed.

Box Tunnel was constructed between December 1838 and June 1841 for the Great Western Railway (GWR) under the direction of Isambard Kingdom Brunel.
Building such a tunnel was considered dangerous at the time because of its length and the composition of the underlying strata.
The main contractor was George Burge of Herne Bay.
For many years, it was rumoured that Brunel had aligned the tunnel so that the rising sun would be visible through it on his birthday, April 9.
On 30 June 1841, it was opened with little ceremony.
When completed, it was the world's longest railway tunnel.

In the build-up to World War II, a military Central Ammunition Depot (CAD) facility was established alongside, reusing existing mine workings.
The GWR established freight facilities including two sidings just outside the eastern entrance to the tunnel to facilitate the movement of ammunition to and from the CAD.
The facility was closed after the war.
During the 2010s, the tunnel was modified to accommodate overhead catenaries as part of the GWML electrification scheme.
In summer 2015, the tunnel was closed for preparatory work including lowering the track.
Box Tunnel passes through Box Hill on the Great Western Main Line (GWML) between Bath and Chippenham. The railway tunnel is 1.83 miles (2.95 km) in length, straight, and descends on a 1 in 100 gradient from its eastern end. The west portal is Grade II* listed and the east portal is Grade II listed.
Box Tunnel was constructed between December 1838 and June 1841 for the Great Western Railway (GWR) under the direction of Isambard Kingdom Brunel. Building such a tunnel was considered dangerous at the time because of its length and the composition of the underlying strata. The main contractor was George Burge of Herne Bay. For many years, it was rumoured that Brunel had aligned the tunnel so that the rising sun would be visible through it on his birthday, April 9. On 30 June 1841, it was opened with little ceremony. When completed, it was the world's longest railway tunnel.
In the build-up to World War II, a military Central Ammunition Depot (CAD) facility was established alongside, reusing existing mine workings. The GWR established freight facilities including two sidings just outside the eastern entrance to the tunnel to facilitate the movement of ammunition to and from the CAD. The facility was closed after the war. During the 2010s, the tunnel was modified to accommodate overhead catenaries as part of the GWML electrification scheme. In summer 2015, the tunnel was closed for preparatory work including lowering the track.
Box Tunnel