We're underneath the city of London, 70 feet underneath it to be exact, and we're standing

on the edge of a railway platform.

It looks a little bit like we're about to get on the tube, but on second glance, the tunnel

extending off into the distance is a little bit small.

And as workers are milling around, killing time with darts, and then a train chugs in

the view.

But the train has no conductor, it has no riders, there's no people on it at all, and

the train is really small.

It's this caterpillar of carts that reach about waist height, but instead of seats, each

of its carts is piled high with giant lumpy cloth bags.

The workers spring into action, they hoist the bags onto their shoulders and toss them

off to the side, and in a flash, the train whisks away again.

I'm Dylan Thoris, and this is Atlas Obscura, a celebration of the world's strange, incredible

and wondrous places, and today we are taking you to London's other underground.

A railway built for one purpose and one purpose only, to keep the city's mail coming on time.

We take a trip on the London Mail Rail, after this.

Shipping these days is an arms race.

Who can deliver the fastest, whether it is groceries or Christmas presents or just a bagel

from the deli on the corner?

The speed of delivery is the name of the game.

Fast isn't fast enough.

Your critical deliveries demand a team that is ready to snap into action.

...