One of the Cemestos prefab homes built to secretly house thousands of Manhattan Project workers.

What may be America's largest classic video game arcade lurks inconspicuously in a Chicago suburb.

World's second largest particle accelerator, where nature reveals its secrets.

The final resting place of the world's first nuclear reactor.

The first commercial nuclear power plant constructed on Long Island.

A famed data visualizer's personal sculpture garden is a landscape of modern and megalithic wonders.

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.

Six tiny houses built for working class people form the largest intentional cluster of Wright homes anywhere.

A solitary tree has grown up all alone on Lake Wānaka, backdropped by the beautiful Southern Alps.

An architect transformed this abandoned cement factory into his castle-like workshop.

Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.

No one's quite sure why there's a metal megaphone bolted on two rocks in the middle of the Mojave Desert.

This park is home to California's first oil boomtown, with structures that have stood for more than a century.

With its webbed walls and bright red coloring, Calgary's iconic bridge looks like a finger trap puzzle stretched across the river.

One of the last remaining buildings from one of Calgary's earliest businesses.

A controversial blue hoop has been puzzling freeway drivers since 2013.

The original place where water met land in the City by the Bay is outlined in brass.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

The United States Capitol's former columns still stand.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

This museum sits on the site of a decommissioned military communications base.

A painfully obvious spy house sits right across the street from the Russian Embassy.

The vaulted ceiling is home to a scurry of “squirrelgoyles.”

The hidden offices underneath Memorial Bridge have been locked up since 1976.