This 16-foot, intricately detailed model of the Gearing-class destroyer has been called the most detailed model ship ever built.

The U.S. Navy’s preposterously detailed mini battleship took 77,000 hours to complete.

One of the largest artillery pieces in the world sits in a Washington D.C. parking lot.

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

The world's first purpose-built motor racetrack was destroyed by the outbreak of two world wars.

The "worst battleship ever built" is enjoying a grand second act, submerged 30 feet in the Gulf of Mexico.

The 44,000-ton aircraft carrier was purposely sunk to create an artificial reef teeming with life.

Nobles would stage mock naval battles on this large lake at the Royal Palace of Caserta.

Remnants of the Nazis' occupation of Denmark linger along the sand.

The last remaining predreadnought battleship in the world has been a museum for nearly a century.

A decommissioned Naval base now rents itself out for people who want to blow stuff up.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

One of the few working locomotive roundhouses in the United States.

The highest waterfall in Italy is only "turned on" five times a year.

This top secret Chinese military megaproject is the world’s largest human-made tunnel structure.

A whimsical village of unique treehouses resides in a Washington forest.

The sinister ruins of one of the worst dam failures of the 20th century lie in this astonishing alpine setting.

This long, dark tunnel is open to hikers, but those without lights are known to get confused even on the straight path.

The site of the Wellington avalanche, one of the America's worst railroad disasters.

This historic little railroad runs through some of the most beautiful scenery in Germany.

An antique narrow gauge railway line still running through the Colorado and New Mexico mountains.

A section of a historic wooden trestle viaduct is preserved next to the railway line it once carried.

These decaying bridges 1,000 feet high are a reminder of the skill it took to cross the Colorado Rockies by rail.

This old train trestle and collapsed tunnel once allowed the railroad to negotiate the steep slopes of the Colorado Rockies.