Canada's oldest railway tunnel is illuminated in a rainbow of color as it passes under the streets of this small city.

One of Mother Nature’s geological gems, home to many prehistoric fossils.

This water-locked cliff face is covered in hundreds of ancient pictographs.

A 400-year-old mummified arm dangles from the ceiling of St. James the Greater, serving as a warning to thieves.

The hidden lair of an alchemist rediscovered in a 2002 flood.

This former quarry is now a picturesque gorge that hides a sunken lake.

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.

Every year, the colorful murals of Montreal get a complete makeover.

These azure waters were thought to lead to the Mayan Underworld.

Underwater art project will double as a massive artificial coral reef to help regenerate the damaged ecosystem.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Every equinox this Maya pyramid puts on a spooky ancient light show.

Hidden in a secluded Greek cove is a pristine beach marred only by the rusting smuggler's hulk stranded on its shores.

The hallucinogenic center of the ancient world.

A spectacular cave and a beguiling lake.

Monasteries on rock pillars, once accessible only by frayed ropes.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

Paris' linguistic guide to the international language of, yes, love.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

This picturesque medieval monastery guards a small trove of historic treasures.

Where the lovelorn find a home for their sentimental keepsakes.

A musical instrument played by the sea.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.