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

Red, white, and blue painted steps along with a Union Jack celebrate the outcome of Gibraltar's 1967 referendum.

Single runway interrupted by a busy road that cuts across its middle.

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

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

This lucky bronze frog was gifted to Madrid by a casino.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

This 19th-century fountain's namesake animal isn't what you think it is.

Giant topiary dog once played a role in a terrorist bomb plot.

Two towns are linked by an engineering marvel masquerading as a boring suspension bridge.

Where the writer penned his famous story about a jumping frog.

The Empire Mine is "one of the oldest, largest, deepest, longest and richest gold mines in California."

Founded in 1873 to support the needs of the gold mines flourishing nearby, this is the last water-powered foundry in the United States.

The tallest bridge in California was constructed for a project that was eventually cancelled.

A sculpture dedicated to Napa Valley's oldest mineral water company.

This historic California cemetery holds the bodies of veterans of both the Civil War and the Donner Party.

A quiet nook at the top of a little-known hilltop park named after California's first poet laureate.

Staircase winds down the side of Telegraph Hill through gardens, wild parrots flying overhead.

A whimsical antique shop with a strong air of mystery, filled with items from ages, and what feels like worlds, past.

Gold Rush ship-turned-hotel buried underneath San Francisco's financial district.

Noble beasts perhaps, but not the Emperor's dogs.

A shining, cold, black organ lies in San Francisco's financial district.

One of the last remnants of the city's Chinese nightclub scene is now a dive bar selling killer mai tais.