San Francisco's most expensive hotel suite includes a secret passageway rumored to have been used by JFK.

Tiki luxury on Nob Hill.

This 19th-century church is now a popular roller rink.

An essential stop before plundering, BYO Cutlass.

San Francisco's newly reopened hands-on science museum.

A 140-year-old castle with underground caves hidden in San Francisco.

Railways may have forged this quintet of lovely tunnels, but now they are open to hikers.

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

This dramatic landscape hidden on the Isle of Skye looks as though you've stepped into the magical realm.

The largest cave chamber in Britain—big enough to fit a whole cathedral inside.

A modern English garden of eccentric beasts, follies, and oddities.

The Origin of On the Origin of Species.

Grotto replete with mystical designs laid out in glued shell mosaics.

One of the few standing Roman lighthouses and a labyrinth of tunnels are a couple of the secrets at this historic castle.

A house of bones — but nobody is quite sure to whom they belong.

This skewed English house has looked like it's going to fall over for centuries.

Numberless clock creates a meal of time for the dreaded, insectile Chronophage.

A treasure trove of astronomical, mathematical, and scientific instruments at Cambridge University.

A rocky sea serpent hides caves, blowholes, and a spectacular natural bridge.

This tangled English forest looks like something right out of a fairytale.

Sometimes an island, sometimes a rocky outcropping connected to the world by a tiny suspension bridge.

A open air theatre built on a cliff by an eccentric British woman.

The largest greenhouse in the world is home to over one million types of plants.

A unique waterfall that some believe attracts the fairfolk.