A modern mechanical planetary system, part of a 10,000 year clock.

San Francisco's oldest operating hotel, with a Victorian atmosphere and a "haunted" fourth floor.

This private residence was the template for one of the most beloved television homes of all time.

Golden Gate Park's historic collection of plants.

Olfactory delights in San Francisco's Botanical Gardens.

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

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

This tiny museum hidden above a restaurant houses thousands of modern and traditional kites.

Trade in that pesky human soul for cold-hard circuits.

An ever-evolving wall of graffiti art off East Liberty Street.

These statues pay homage to the "green corridor" of parks and wetlands.

Three playfully immersive mini golf courses let you travel alongside your ball to the cup at this facility, which has been around since the 1950s.

"Looks so real, it's scary!"

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

On Gellért Hill, this statue depicts the tragic tale of lovers divided by the Danube.

Tucked away near more famous landmarks lies a statue meant to symbolize the confluence and continuing development of human culture.

Launched by Napoleon's soldiers more than 200 years ago, a cannonball remains embedded in the tower wall.

The final resting place for the remains of 143 Habsburg royalty.

In the middle of a Vienna square, Roman ruins dating back some 2,000 years are on display.

Baroque celebration of the end of the Great Plague of Vienna.

Designed as a reminder of one of the darkest moments in Austrian history.

A silly medieval mural preserved on the side of a Viennese house.

An exquisite Baroque church in Vienna's old town.

Op-art architecture designed for happiness.