This historic Pittsburgh tennis complex is a rare example of natural red clay courts.

Pittsburgh's literal underground railroad.

A pride of the state, this working museum crafts pottery mosaics in the style of Pennsylvania's earliest European settlers.

The Cold War-era "underground Pentagon" is a sprawling subterranean hideaway for the Defense Department.

A legendary boxing venue and ring featured in Rocky V.

Within this beautiful Pittsburgh cemetery, a unique headstone bears witness to one man's eternal love for Jaws.

Erected in 1697 this Philadelphia bridge is the oldest surviving roadway bridge and perhaps the oldest stone bridge in the United States.

A local prank turned town icon.

The rusted hull of a WWII German destroyer pokes above the surface in a Norwegian fjord.

Norway's national monument to fallen seamen.

Housing the famous Norwegian ice-defying 19th century polar exploration ship.

A reconstructed farm shows what life was like in Norway 1,500 years ago.

Longest road tunnel in the world features an air treatment plant and the illusion of daylight.

Cold storage for agricultural biodiversity.

This "Palace of Purification" has made many film appearances as a dark and sinister headquarters.

This Toronto garden collects stares and tchotchkes in equal measure.

Puerto Rico's once thriving oil company is now an abandoned wonderland of rusty steel.

These red and black houses were awarded to the firefighters who saved their city from an enormous blaze.

This giant bronze image of Christopher Columbus embarked on a voyage of its own.

This bleach-white graveyard overlooking the ocean is accessed through a tunnel.

These light, hollow rolls have been linked to Acadia National Park since the 1890s.

Abandoned Italianate architecture on the coast of Maine.

The only remaining historic maritime signal station in the United States.

Maine’s only official memorial to the Underground Railroad.