There is a legend in London, England, about the 'greatly large and deep underground tunnel'.
It was this large tunnel that began to destroy the Second World War air defense system in 1930.
While drilling a tunnel during the construction of the tunnel, you will find a large hole deep underground and begin to explore.
But!! Not reaching the end of the tunnel, all explorers die of disease.
Still, the mysterious identity of the tunnel has not been revealed, and it has not even been revealed who built such a huge tunnel, when and how it was built.