This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

Hidden beneath a beautiful overlook you’ll find the history of the city depicted in comic strip format next to a pay toilet.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

The ruined doorway is a portal to the building's turbulent and torturous past.

An ancient octagonal weather station named for the eight Greek gods of wind.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

The railway carts travelers to central Athens's highest peak, which offers stunning vistas of the city.

A collection of 20th-century automata, penny arcade games, and musical contraptions.

San Francisco's newly reopened hands-on science museum.

A psychedelic labyrinth on the San Francisco bay.

The second building of its name to occupy this location might be the finest flatiron building in San Francisco.

A still functioning vaudeville carousel that has operated for over a century boasts a colorful menagerie and past.

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

This one-block alleyway is stuffed with street art that is colorful, cultural, and intensely political.

This playground sculpture of an icon from the past is dedicated to the children of the future.

A beautiful footbridge with over 2,000 glass sculptures along the walls and ceiling.

The U.S. Navy's last diesel-electric submarine rests half-submerged in the middle of Portland.

The only surviving piece of a submarine said to be the most decorated vessel in U.S. history.