Chislehurst Caves
London Borough of Bromley, United Kingdom
The Chislehurst Caves are a series of intersecting man-made tunnels and caverns covering some 22 miles (35.4 km) in Chislehurst in the London Borough of Bromley. Today the caves are a tourist attraction and, although they are called caves, they are entirely man-made and were dug and used as chalk and flint mines. The earliest recorded mention of the mines and lime-burning kilns above dates from a 9th-century Saxon charter and then not again until around 1232AD; they are believed to have been last worked in the 1840s. From the mid-13th to early 19th centuries the "caves" were created and expanded from the mining of raw chalk, flint and lime-burning chalk. During World War I the caves were used as an ammunition storage dump associated with the Royal Arsenal at Woolwich. In the 1930s the tunnels were used for mushroom cultivation.
Mine data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).