This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A moody and picturesque riverside ruin overgrown with vegetation.

Petrified footprints of one of the very first vertebrates to walk on land.

Graffiti from the 16th and 17th centuries cover the walls of this part of the Tower of London.

This knockout museum lies in a sleepy corner of London.

More than a million titles fill the labyrinthine shelves of this prestigious private library.

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.

This hospital helped pave the way for treatment that drove down child-mortality rates in 19th and 20th centuries.

A unique tribute to the millions of animals who served and died for the British military.

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

A building that survived WWII, possibly on the virtue of its name alone.

London's only public statue of the much-married monarch adorns the gate to St Bartholomew’s Hospital.

The 2,000-year-old beam is tucked within the pedestrian entrance to the old London Bridge.

A sculpture outside London's oldest cathedral honors the Mohegan chief who died while petitioning the king.

The canine-themed book collection claims to be Europe's largest dog library.

A plaque marks the underground site of one of London's "lost rivers."

This 1920s Dutch barge is now a floating bookstore.

The British monarchy's stamp collection is one of the most impressive in all of Europe revealing generations of royal nerdery.

The remains of an ancient Roman teenager are memorialized at the base of a modern London landmark.

The Florence Nightingale Museum is home to the famous nurse's most treasured possession: her beloved pet owl.

Two plaques commemorate the site of Shakespeare's first theatre.

A community of artists and entrepreneurs seeks a simpler life on London's waterways.