One man's remarkable private collection of art from around the world.

This tower once served as a radar station during the Cold War.

A brutalist gem towering over the heart of Milan.

Saint Borromeo often prayed in this austere crypt during the 16th century.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

Breathtaking and huge 430 year old maps of Italy.

Some 4,000 individual tiles make up this striking blue billboard from the golden age of air travel.

Eat the ultimate iteration of Portugal's most beloved pastry.

Sip cherry liqueur at a bar dating back to 1840.

Visit a surreal landscape so otherworldly NASA actually used it to train the Apollo 17 crew.

Partially collapsed lava tube and cave system complete with concert hall, underground pond, and unique albino crabs.

This historic electric train has operated with regularity since the early 1900s.

This local emblem is the oldest and largest dragon tree in the Canary Islands.

This beautifully verdant lagoon is tucked below a massive volcano in a crater atop a black pebble beach.

Legend has it that this bronze orb, which sat atop an ancient Egyptian obelisk, once held the ashes of Julius Caesar.

Two very green residential towers cleaning the air in one of Europe's most polluted cities.

Beneath the southern end of the Golden Gate Bridge is the “Gibraltar of the West Coast,” a fort built to protect the San Francisco Bay from naval attack.

At the base of the Golden Gate Bridge, a small sign basically begs for a high-five.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.

San Francisco's urban bison herd has persisted in the face of extinction, development, and disease.

A huge musical instrument played by the ocean.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

Golden Gate Park's historic collection of plants.

Relics of the 1894 Midwinter Exposition continue to delight visitors today.