Hidden beneath the streets of London is a secret subway that only carried mail.

A 142-foot-tall Q-tip on Bristol's skyline.

A gargantuan crystal kingdom.

The remains of a British railway rusting in the jungle mist of a Brazilian mountainside.

A 19th-century time capsule of travel, fiction, and historic texts still available to the public.

A tiny, hidden alleyway dedicated to the father of meteorology.

Despite having a dome made of papier-mâché this tiny observatory has survived for over a century.

A Victorian Gothic masterpiece housing a world-class collection of rare books and manuscripts.

An alleyway plaque is all that remains of the independent Texas' envoy that forgot to pay their rent for over a century.

The signs of a long buried road can still be found hidden beneath a London sewer grate.

The largest of London's subterranean rivers and once a mad, bad center of London life.

An unusual round church in London with a Templar past.