The maritime museum that boasts the largest nautical library in the western hemisphere.

America's first public mental health facility.

This once-palatial plantation may have been the site where a draft of the Declaration of Independence was written.

An enormous warehouse filled with parade floats collected from over 50 years of patriotic celebrations.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

The ruins of this Thomas-Jefferson-designed mansion have been left to crumble since the Christmas Day they burnt down.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

Exact replica of the ancient monument, but much, much lighter.

A former major munitions plant that has been converted into a sprawling art space.

Home to items never before seen by the public.

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

Berkeley Hot Springs presents to you "the only outdoor monument to presidential bathing."

A tradition unlike any other, this marks the site of the annual Groundhog's Day tradition.

A dramatic, 360-degree recreation of Pickett's Charge in the Civil War.

A local prank turned town icon.

A toxic ghost town sitting atop a massive coal fire.

Sail through this subterranean show cave that is home to a legend that would go on to name nearly everything around it.

This monument to one of the largest science fiction games of all time bears the names of hundreds of thousands of players.

This stunning concert hall has become a symbol of Iceland's national recovery.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

The picturesque birthplace of Icelandic democracy is drenched in the blood of its brutal past.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.