France's national museum of scientific and industrial instruments.

An overlooked marble is the only surviving in-place 18th century example of the measurement that changed how we define distance.

Saintly bones pressed into a wax effigy of a Catholic superstar.

This mural painted by Keith Haring was done without payment as a gift to entertain the children at the Hôpital Necker.

The mummified heart of Louis XVII, the lost dauphin of the French Revolution.

The site of slaughterhouses that once satisfied Parisians' taste for horse meat is now home to a park and book market.

A 19th-century funicular railway shuttles visitors up this surprising sea cliff to one of the world's largest camera obscuras.

This enormous secondhand bookstore inside a Victorian train station sparked the "Keep Calm and Carry On" craze.

The sign at the garden gate reads: “These Plants Can Kill.”

This iconic 1,000-year-old medieval castle is a favorite of the film industry, most notably as the location for Hogwarts in Harry Potter.

One of the few surviving examples of Victorian-era public toilets now houses a small homestay.

A tongue-in-cheek arcade where the games are based on everyday life.

Museum dedicated to the UK's first charity for abandoned children, with keepsakes of the mothers who left them behind.

The Tudor-style cottage in the middle of the square is not quite what it seems.

This intriguing Bronze Age artifact spent centuries hidden within a Welsh faerie hill.

Buried for centuries, this hidden cellar is all that remains of London's medieval Whitefriars Monastery.

Dictionary Johnson’s favorite feline.

An unusual round church in London with a Templar past.

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.

The fierce beast perches atop a pedestal marking where the historic City of London gates once stood.

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

This inn of the court provides a fascinating window into London’s legal and architectural history.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.