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

This palatial botanical garden is home to one of the largest pipe organs ever installed in a private residence, and a piece of Wood's cycad.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

Most-visited and most-photographed slot canyon in the American Southwest.

Dramatic river bend surrounds a natural red-rocked pedestal.

An eerie collection of the surviving structures from a past celebration of the future.

Possibly the oldest church in Barcelona, this basilica has its pagan and Christian mythologies all mixed up.

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

This macabre painting of a Shakespearean scene looks like something out of a nightmare.

Holy Grotto of Montserrat Monastery holds one of Europe's mysterious black Madonnas.

Legend says these colorful, invasive residents are the descendants of birds released by Jimi Hendrix.

This unassuming alcove in London’s famous Tower Bridge once served to capture, store, and display dead bodies from the River Thames.

Richard III supposedly disposed of his nephews' bodies here in an effort to seal his claim to the throne.

According to the legend, this strikingly beautiful hill has miraculous healing powers.

One of Ireland's most infamous prisons for rebels including men, women and children.

A remarkably intact castle that once was the largest in Ireland.

The ruins of an 800-year-old monastery boasts the tallest round tower in Ireland.

The ruins of a monastery that dates to the 7th century.

Giant eggs, walls of bread, and nightmare surreality mark the largest collection of works by Salvador Dalí.

These fly sculptures are scattered around the city and represent the patron saint of Girona.

Designed by Gustave Eiffel before his famed tower.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

The modern birthplace of Irish freedom.

Catacombs turned marketplace.