There is a veritable city's worth of tunnels underneath London. Many of these tunnels are secret tunnels, decommissioned military tunnels, decommissioned subway tunnels, postal tunnels, and much more.

When the Royal Mail wanted to make faster deliveries around London in the early 20th century, the Post Office Railway was their solution. According to Atlas Obscura, the system was inspired by Chicago ...

Subterranean London's post office railway – the historic Mail Rail – is about to be torn down and transformed into a tourist attraction. "The air has been so still down there that stalactites have ...