This 19th-century island fort built to protect against an invasion by sea.

An 800-year-old island castle in Guernsey's main harbor.

An intricately decorated tiny place of worship.

A Byzantine-era church hidden in a wooded area below the Acropolis.

Legend says this sacred tree was a gift from goddess Athena.

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

Ancient serpentine sacrifice holder that has stood the test of time.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

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

Legend says if you stick your thumb in the hole and it gets wet your wish will be granted.

No one is sure if the world's fourth-largest diamond had been found in a rubbish heap or was pawned by Napoleon's mom.

1513 Turkish world map, full of European state secrets and snarky commentary.

This crumbling medieval basilica once attracted pilgrims by the thousands to collect a miraculous dust that formed above the saint's tomb.

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

The alleged house of the Virgin Mary is tucked away in a park and nature preserve on Mt. Koressos in Turkey and is holy to both Catholics and Muslims alike.

The world's most active stratovolcano is almost always erupting.

This statue of the great Argentinian car driver is located near a famous curve of the Monaco Grand Prix.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

Amsterdam's narrowest house facade is a monument to 17th-century tax evasion.

A grand Gothic Revival basilica with stained glass depictions of Montreal's religious history has only one soul resting in its crypt.

Designed by Buckminster Fuller, this relic of the 67 Expo survived fire and ice.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

A monument celebrating the idea of reaching inaccessible places.

Rumored to be the famed pirate's lookout tower, this historic stone structure is now just watching for tourists.