This cathedral dedicated to Louis IX, sainted King of France, holds many secrets.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

135 bronze medallions mark a French meridian line which once rivaled the hotshot Greenwich timeline.

Site of a classic 19th-century physics experiment to prove the earth is rotating.

This modest marker near Notre Dame identifies the very center of Paris.

This demon atop the Notre-Dame de Paris looks utterly bored.

Five candy-colored villages on the Italian Riviera.

A lover's walk between hilltop towns, decorated with graffiti love notes.

The bomb-ravaged remains of of a colossal Neptune.

This extinct volcano rises above Edinburgh and is special for its panoramic views over the city.

A bronze statue of a low three-legged seat commemorates a piece of furniture that started a riot.

The 20th-century chapel’s intricate woodwork includes amazing details, most notably angels playing bagpipes.

This ancient Irish religious site is covered in ancient carvings, many of which have barely aged.

These imposing walls and towers look more like the ruins of a fortress than a monastery.

An enigmatic monument to the Irish revolutionary who plotted an uprising against British rule.

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

Inspired by Thomas Stothard's painting of the "Journey to Canterbury," albeit with Canterbury natives.

The final resting place of the great navigator, or maybe his brother.

A serene plaza that commemorates one of the Granite State's most iconic figures.

The Old Man of the Mountain’s less-famous, but still beloved little brother is said to resemble a leader of the Abenaki tribe.

Come for the gun-toting hillbilly madman, stay for the ice-cream loving basketball bears.

A magnificent waterfall nestled in the heart of the El Yunque National Forest.

This colorful gate stands as an entrance to the walled city of Old San Juan.

One of the last remaining movie theatres in the country that features a rear-projection system.