One lonely, modern pyramid has gone from corporate think tank to deserted boondoggle.

From overly ambitious (and eventually abandoned) atomic dream to bustling office park.

These World War I shooting range tunnels are now haunted halls of underground graffiti accessed through the roots of a tree.

Jacksonville's highways rendered this century-old grammar school unusable.

A century-old network of freight tunnels underneath the city's historic business district.

Ruins of the elaborate house where the enigmatic costume designer threw glamorous parties for New York's theatrical elite.

The span is crooked and made from two older recycled bridges.

This deserted Gold Rush town is home to a Masonic lodge that, strangely enough, still holds meetings.

An abandoned, decaying sculpture garden built by an eccentric physician in the 1920s now looks more like a forgotten cemetery.

The short-lived railroad town in central Oregon has been abandoned since the 1930s.

The century-old remains of an abandoned farm town in eastern Washington.

Buffalo's abandoned concrete grain elevators are getting a second life.

The location of Puerto Rico's first water bottling plant, thanks to a collaboration between Mother Nature and technology.

A castle inspired by medieval architecture is hidden in the woods of Connecticut.

An overgrown and abandoned tuberculosis ward resides in the midst of a quaint modern neighborhood.

A handful of beehive kilns are all that’s left of a historic brick-making empire.

A hillbilly theme park that proved so unpopular the land wouldn't even sell on eBay after it closed.

A well-preserved Ancestral Puebloan ruin tucked beneath a desert cliff.

A theme park that suffered massive flooding during Katrina was abandoned, and now proves irresistible to trespassing explorers.

A library of poems cascade off the branches of this unsuspecting tree.

Abandoned concert venue legendary for its rock counterculture.

An eight-sided home built during a brief octagon craze in the 1850s.

During WWII the U.S. Navy conducted primitive drone strikes on this Lake Michigan lighthouse.

The deserted railroad town had a last gasp as a ghost town attraction before being abandoned for good.