Once home to the country's most gargantuan ships, this graving dock now waits for people to buy furniture.

An abandoned subway tunnel that could have reinvigorated Staten Island still lies somewhere beneath this Brooklyn park.

A colossal floating restaurant built to look like a ancient Chinese imperial palace.

The home of aviation trailblazers, in a remote corner of the big city.

This abandoned seaside fortress is now simply an imposing ruin being taken back by nature.

Current docking place of the SS United States, the fastest transatlantic ocean liner.

A scenic fort on the harbor protected Philadelphia from an attack that never came.

A National Historic Landmark with a scenic clock tower and park filled with deer and peacocks, plus a military museum.

Fighting the British and making game shows for over 150 years.

A crumbling island fortress that seems to be covered in a field of stone crosses but is simply incomplete.

A castle-like sea fort from the 17th century is now a museum to oyster farming.

Surreal riveted sea forts once protected the Kent shores from German attack.

Once America's longest-manned military fort, now an abandoned hulk.

A lone gunner's station is all that remains of a replica Spanish Fort in Florida.

This sprawling Belgian fort was once thought of as impenetrable but now it is simply an abandoned relic.

This historical Netherlands fortress still bears the marks of its single siege.

Anyone wanting to know what a dwarven mine sounds like need only visit the tunnels of this New Zealand artillery compound.

The home of one of America's most beloved fictional characters has become a real world landmark.

Captain America, Sub-Mariner, and the Human Torch were all born in this art deco Manhattan masterpiece.

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

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

Only hotel where you can legally launder money.

Early prototype for Frank Lloyd Wright's Guggenheim.

Nestled in the heart of San Francisco’s bustling Financial District stands a unique homage to the Mayan and Beaux Arts.