Watford Tunnels
Watford Tunnels are a pair of railway tunnels on the West Coast Main Line just north-west of Watford in Hertfordshire, Eastern England. The original was built in 1837 for the London and Birmingham Railway to the design of Robert Stephenson and is just over a mile (1.6 kilometres) long. When the line was widened in the 1870s, a second tunnel was built just to the east. Both tunnels had decorative portals and the south portal of the original tunnel is a Grade II listed building.
Tunnel data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).