An experimental forest at the foreground of arboreal science is also the canary in the coal mine for climate change.

The arch that celebrated the completion of the Lincoln and Victory highways.

This beloved roadside attraction welcomes visitors with his signature neon smile.

This former monument to an invented Iraqi victory was turned into a military camp during the subsequent invasion.

A giant bisected onion dome remembers the Iraqis who died in the Iran-Iraq War.

Lombard Street may be more famous, but this is the real “crookedest street in the world.”

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.

An elaborate gift from Claus Spreckels is now a piece of San Francisco history.

This grinning pup statue is all that's left of what was once a ubiquitous Bay Area diner chain.

The only visible piece of San Francisco's most famous shipwreck.

A garden oasis filled with flowers mentioned in the works of William Shakespeare.

Golden Gate Park's historic collection of plants.

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

Olfactory delights in San Francisco's Botanical Gardens.

A 140-year-old castle with underground caves hidden in San Francisco.

Not far from the busy city lie these remains of a time when the world was on fire.

Tucked away in a downtown Stockholm park are the remains of a World War II defense position.

Finally reunited, the three effigies now stand in a museum courtyard.

A former suicide bridge is now accumulating symbols of love instead of a body count.

This gem from the industrial age helps visitors and residents alike traverse hilly Stockholm.

A king's bloodstained shirt is among the gruesome collection of artifacts displayed below Stockholm's Royal Palace.

Outside a Viking museum sits a modern-day runestone made by a Swedish runemaster using traditional methods.

Stockholm's narrowest alley is barely over two feet wide.

This Stockholm light tower can be controlled by anyone with a smartphone.