The 80-foot tire that looms over Michigan's I-94 was once a Ferris wheel in the New York World Fair.

Inside the Wayne County airport is an amazing collection of lights and sounds.

The park is home to the United States's only still-operating Dutch windmill.

Largest tulip festival in America, includes fireworks, a parade, and a carnival.

With over 5,000 champions, the Hall of Fame continues to draw amateur eaters.

An angular maze of concrete in Grand Rapids acts both as public art and as a staircase for fish traveling upstream.

These sprawling mines once served as a source of plaster and today serve as a storage facility.

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

This magnificent castle grew from a small Moorish fortress, and reportedly inspired two iconic Disney castles.

The former home of a conniving 17th century politician is now a high-end hotel.

Of the many chalices in the running for the Holy Grail, this one in Valencia Cathedral sure looks the part.

A curious carving hides on a marble column in the Mosque-Cathedral of Córdoba.

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

The world's largest wooden structure.

This sculpture pays homage to the street sweepers of Madrid since its inauguration in 2001 in Plaza Jacinto Benavente.

Dr. Fleming's work saved the lives of many bullfighters thanks to his discovery of penicillin.

A neighborhood represented by an apparent geocentric and flat-earth model of the Solar System is hidden in the subway of Madrid.

A haven for book enthusiasts across the street from Retiro Park.

This little sun pays homage to a massive gate that once stood at this location.

For decades, Puerta del Sol has been illuminated by a giant, guitar-wielding bottle of sherry.

This unassuming bookstore in the heart of Madrid is one of the oldest in Spain.

A stone slab in Madrid marks the point from which the distances of Spain's national roads are measured.

Just like in Hollywood, Madrid has also a forgotten walk of fame.

This sweet-toothed bear searching for snacks has been a symbol of Madrid for decades.