A 10 million-ton rock once worshiped by the Tahamies Indians, accessed by an astounding staircase.

Founded as a refugee camp, now a popular tourist spot.

This underground church is topped with a 500-foot cross that is seen by many as a beacon of fascist hubris.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

Spain's unique Mosque-Cathedral has been a place of worship for both Muslims and Christians throughout its history.

The oldest restaurant in the world is this old-world Spanish eatery, still known for its suckling pig.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

This ancient Roman bridge and aqueduct still stands as a wonder of classical construction.

The famous winding walk at Chartres is surrounded in mystery and myth.

A complex of six forts embedded in the Rajasthan hills.

The most confusing clock in New York.

The site of the deadly Triangle Shirtwaist Factory Fire.

Avoid gangster interaction while window-shopping.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The celebrated eyesore created by starry-eyed sweethearts.

A museum on the history of Paris, including a set of Napoleon's toiletries, Proust's room, and relics of the Revolution.

France's most famous cemetery, with some of its most curious tombs.

The sister plane of the C-123 shot down during the Iran-Contra Affair has found a new purpose in retirement.

These mysterious ancient stone spheres were created by a civilization lost to time and are now mostly lawn ornaments.