These magnificent city walls rise from the barren sun-baked Spanish plains like something straight out of a fairytale.

Science meets wall art to highlight the beauty of famous mathematical equations.

This underwater cave in Madagascar is home to what is thought to be the country's largest fossil graveyard.

Beautiful antiques and obscure engineering artifacts trace the evolution of phones from rare luxuries to ubiquitous.

The medieval network of canals hidden underneath the city is opened to explorers each year.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

"the sweltering inhabitants of Charleston and New Orleans, of Madras and Bombay and Calcutta, drink at my well . . . The pure Walden water is mingled with the sacred water of the Ganges."

A whimsical, but often overlooked clock in Park Avenue.