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

The unique traffic pattern named for an influential urban planner is also known as the Pedestrian Scramble.

When it opened during the final years of the embargo, all the drinks and cigars were free.

People escaping slavery may have hidden inside a corpse vault.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

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

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

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

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

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

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

The United States Capitol's former columns still stand.

Home to items never before seen by the public.

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

Constant erosion has created a surreal landscape of bleached and preserved fallen trees.

Elvis's own personal tropical hideaway.

Walk the whole Mississippi River!

A railroad tunnel that, upon its completion, was considered one of the engineering marvels of the modern world.

The flower-shaped temple in Virginia aims to transcend the boundaries of the world’s religions.

Near-constant high winds deform the trees on Spruce Knob, the highest point in West Virginia.

An office built to look like a giant basket.

A flamboyantly decorated bridge signals diversity and fellowship at the entry to Indianapolis' Broad Ripple Village.

A favorite of Amelia Earhart, ranking among those rare bridges that can be crossed without changing sides of the river.