The secret medieval tunnels that we still don't understand

Crossposted from digg /interesting

Around 2,000 strange tunnels have been found around central Europe. These aren’t like the well-known catacombs of Paris or Rome. Known as the erdstall, these passages are extremely narrow, never more than two feet (60 centimetres) wide nor high enough for an adult to walk in, and sometimes the passages become seemingly impossibly narrow, as small as 16 inches (40 centimetres) in diameter. Determining their age and purpose is made difficult by the fact that almost no archaeological evidence has been found inside any of them. A ploughshare was found in one, millstones in a couple others, but apart from that the erdstall are eerily empty. Carbon analyses of coal and pottery fragments found within point to construction dates of around 900 to 1200 AD, but no written records from the Middle Ages mention the erdstall’s existence.