This week we're going underground - with a theme of tunnels and caves around the country.
The Big Pit National Coal Museum at Torfaen, Wales, was an active coal mine from 1860 to 1980, and then re-opened in 1983 as a fascinating museum of Wales' mining heritage. The Coal Museum is part of the Blaenavon World Heritage Site
Sandstone caves at Kinver Edge, near Kidderminster, were home to 44 people until the 1960s. They became a tourist attraction over a century ago and still make a fascinating visit.
A glimpse, perhaps, of an industrialised farming future lies far below the surface of London. Out of reach from any fresh air and sunlight, the Growing Underground project uses innovative LED lighting to grow produce in a former World War II bomb shelter.
Anyone travelling by train through Sussex on the Brighton Main Line from London will surely have noticed the Clayton Tunnel between Hassocks and Preston Park railway stations. With its turreted and castellated north portal, it is a charming and whimsical sight, but has a tragic history.
The Hellfire Caves are a network of man-made chalk and flint caverns which extend 260m underground near High Wycombe in Buckinghamshire. They were a meeting place of the Hellfire Club in the mid-1700s - an association of upper class rakes and radicals.
Mice are well-known for their adaptability to survive in different environments. But London's Underground must be one of the most unnatural for them imaginable. Yet the mice thrive ...
