The oldest working mechanical clock in the world.

A castle in the Scottish Highlands has been continuously inhabited since the 1300s.

One of England's most famous churches hides a pair of little known architectural treasures.

The most loyal of little dogs, or a Victorian era publicity stunt?

A fantastic castle rumored to be the birthplace of King Arthur.

Hear the quietest sound from across the dome.

An unusual round church in London with a Templar past.

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

Famously misunderstood wonder of the ancient world

These little castles each held thousands of pigeons.

17th century mosque for Shah Abbas' harem.

Named after a legendary garden called Eram in southern Arabia, built by order of Shaddad, an Arab king who wanted to compete with Paradise.

This 17th-century structure is a beautiful testimony to traditional Persian architecture

The enormous 250-room Vanderbilt mansion conceals hidden doors and secret passageways.

This palatial botanical garden is home to one of the largest pipe organs ever installed in a private residence, and a piece of Wood's cycad.

An exquisite collection of fairytale conveyances that puts most car museums to shame.

One of the largest Roman settlements in Portugal.

A stunning 18th-century site where pilgrims ascend by a series of punishing stairs only to return via funicular.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

The ancient latrines of the Greeks, in all their public glory.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.