A preserved block of timber buildings from the city's industrial era in the Middle Ages.

A pre-Industrial Age iron furnace and the site of a nearly-forgotten piece of Black history.

The last holdout of a pre-Civil War rebel who took the matter of slavery into his own hands.

The Kirkland Monument remembers a selfless Civil War hero who braved the battlefield to give water to his dying enemies.

Captain John Smith thought these cliffs were amazing in 1608 but sharks thought so 20 million years before him.

This pre-Revolutionary War grist mill ground corn and flour for soldiers in seven American wars.

It's not hard to see why the historic Peabody Conservatory of Music's library has been described as a "cathedral of books."

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

A secretive collection featuring objects that were designed specifically for U.S. intelligence operations.

An astounding collection of medical specimens, including bits of President Lincoln.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

Largest Roman Catholic church in North America.

The house where John Wilkes Booth conspired with his co-conspirators.

Home to items never before seen by the public.

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

A young botanist's horticultural vision realized through a lifetime of planting, tending, and collecting seeds.

A walk through the historic city center, under the streets of Seattle.

Known as "The Hill of the Little Devils."

One devoted couple has donated multiple recreations of Michelangelo's sculptures to this South Dakota town.

This dramatic sea spire is home to the world's rarest insect and is part of the lost continent of Zealandia.

A narrow strip of land is home to the tallest migrating dunes in Europe.

The remote outlaw hideout of Jesse James, Butch Cassidy, and the Sundance Kid.

This shallow pit was once used to send over 20,000 buffalo plummeting to their death.

This historic cliffside mansion uses a natural cave for air conditioning.