Bizarre Cavern.

According to local history, this cast-iron canine was nearly melted down for bullets during the Civil War.

Historic barracks utilized during both the Revolutionary War and the Civil War.

This hidden treasure provides a charming access point along the south side of Baker Park.

The tragic tale of the dentist who pioneered the use of anesthesia.

This sculpture commemorates the first instance of an American president pardoning a turkey.

The former location of a platform that allowed passengers to safely wait for the trolley.

Commemorating the "Little Giant" who ran for the presidency.

The oldest place in Hartford is a cemetery with thousands of bodies stacked beneath the grass.

The former home of the man whose radical ideas changed the nation.

This historic bridge connects Whidbey Island to Fidalgo Island across whirlpool-filled waters.

Before founding the American Red Cross, Clara Barton had a tremendous humanitarian impact by locating thousands of missing soldiers.

Engraved in stone here are the signatures of everyone who signed the Declaration of Independence.

The "Key of Keys" for Washington, D.C. and the apocryphal landing place for the military campaign that started George Washington's career is now at the bottom of a well.

A gift from Japan, 17th-century lantern stands among the cherry trees at D.C.'s Tidal Basin.

Decades before the scandal, this staircase on the river was a literal "water gate."

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.

The house where Lincoln drafted the Emancipation Proclamation.

This bridge over D.C.'s Rock Creek Park is sometimes called the "Buffalo Bridge" because of its four buffalo sculptures, which were cast from a single piece of bronze.

The innocent intentions of this monument are somewhat lost in the sculpture's muscled imagery.

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

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

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

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