This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

The country's oldest continually-operated mini golf course lies hidden in plain sight, eclipsed by one of D.C.'s most popular tourist attractions.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

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

A wondrous old library overlooking the nation's capital.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

A historic neighborhood church is reborn as a psychedelic arts collective.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

The site of the climactic scene from the classic horror film is now a historic landmark.

The oldest still-existing mosque in the United States sits in a remote prairie in North Dakota.

One North Dakota man's vast collection of rare rocks, polished orbs, and geological wonders.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

This rare wildlife haven in Singapore feels like you're in the tropical rainforest.

Relax on your veranda and watch the light show.

The largest pool at its elevation sits on top of one of the most expensive resorts in the world.

Singapore's landscaping project is home to 18 incredible Supertrees.

Teeming with illegal goods and services, this towering maze of vice is also a popular tourist accommodation.

In Hong Kong, a fairytale flower tunnel is hidden within the gardens of a public housing complex.

The world's longest outdoor covered escalator system transports commuters through Hong Kong's hilly terrain.