A massive underwater sinkhole made famous by Jacques Cousteau.

The deadliest diving spot in the world is also a stunning geological marvel.

The once great capital of Egypt now crumbles forward as evocative ruins.

Where Nor'easters go to die.

Huge masonic hall in Philadelphia with lavishly themed rooms.

Current docking place of the SS United States, the fastest transatlantic ocean liner.

Fascination continues to surround one of history's most infamous shipwrecks.

Cuba's historical trains remind natives of their country's sugary sweet past.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

The kind of mixed-up place that drives archaeologists crazy.

It houses the remains of a 17th-century version of the Titanic.

This iconic fortress was once the crown jewel of Haiti's national defense.

The house that birthed The Old Man and The Sea is now a museum devoted to the old man who wrote it.

A set of ancient drawings in the desert of Peru that are so massive, many of them can only be fully seen from the sky.

The largest stone moai on Rapa Nui.

Famously misunderstood wonder of the ancient world

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

Bordered by forest on three sides and the ocean on the other, the Great Dune of Pilat is the highest sand dune in Europe.

This futuristic observatory at the top of the Pyrénées offers unrivaled views.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

One of Ireland's most infamous prisons for rebels including men, women and children.

This single room has survived the centuries with almost no deterioration.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.