This long, dark tunnel may look old, but back in the 1940s it was home to something more modern: the precursors of radar technology that were being used by the British Army.
The facility, situated beneath the White Cliffs of Dover on the UK's south coast, have recently been opened to the public by the National Trust. Known as the Fan Bay Deep Shelter, it was built in just 100 days at the request of Winston Churchill, providing 400 square yards of space -- enough to house four officers and up to 185 men during the war. The tunnels were home to a set of sound mirrors -- an early precursor to radar -- which were used to detect incoming aircraft.
Decommissioned in the 1950s and filled with rubble in the 1970s, National Trust began restoring the tunnels in 2012. They're now open to visit, if you're ever in the south of England.
Picture: National Trust/Barry Stewart