This Arizona observatory is famous for investigations into Martian life, and as the place humans first spotted Pluto.

The final resting place of the businessman-turned-astronomer who helped discover Pluto stands near his observatory.

A mass grave for victims of an airline disaster that led to much-needed safety improvements for commercial flights.

The wreckage of a World War II bomber is hidden high in the Colorado wilderness.

One of the most accessible undersea plane wrecks in the world.

Hidden amid a collection of trails is the site of a tragic crash.

A sign marks the plane crash that caused two nuclear bombs to fall in North Carolina.

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

The remains of the worst military aviation accident in Canada's history.

The debris forms a solemn memorial to those who died in a 1963 accident.

One of the deadliest American air disasters is nearly forgotten in Brooklyn.

The site of one of history's most indelible and horrific tragedies.

A Japanese pilot crash-landed on this Hawaiian island after the Pearl Harbor attack and terrorized locals for a week.

Deadly airliner crash preserved for those willing to climb and pay respects.

An abandoned aircraft sits submerged in a lake in the Alaska wilderness.

Mysterious wreckage of a small plane has been lodged in this tree since at least 1971.

In a small courtyard resides this large mural that draws inspiration from Leeds and its history.

The last gas-lit cinema in the United Kingdom, and perhaps the world.

Artists have long been drawn to these atmospheric 12th-century ruins.

This Gothic castle-like portal is a testament to the amazing craftsmanship of the navvies who built the railway tunnel.

Railways may have forged this quintet of lovely tunnels, but now they are open to hikers.

The symbol was surreptitiously built into the river bank by German prisoners of war.

Hidden in the New Mexico desert southeast of Roswell, nine small deep lakes formed inside sinkholes.

This fast-food outlet is the only space and UFO-themed McDonalds in the world.