An existential riddle in the world's largest ancient castle.

This remote fort on the Yukon River is a vestige of the wild Alaska gold rush.

Electronic inventions that resulted in products and systems we use every day are on display in this labor-of-love museum.

Fascinating museum dedicated to the under-appreciated medical history of urology features some wince-inducing devices.

In Kazakhstan, a colorful cathedral with many lives once survived the most powerful earthquake in the region.

The taxidermy remains of the mighty beast made famous by a Crocodile Dundee film.

Over 600 acres of idyllic open grassland honor Nebraska’s georgic storyteller.

The first permanent memorial to a unique secret weapon of World War II.

Volcanic stone sentinels stand watch at a Korean Bell Garden in Virginia.

A somber monument commemorates the site of a Native American reservation marked by suffering.

The final resting place of a controversial man who was instrumental in plucking the banjo from obscurity.

There’s a hidden military meme engraved on the World War II Memorial.

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

The most decorated dog of World War I is preserved in the Smithsonian.

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

The final resting place of the living embodiment of the famous Forest Service symbol.

Lines from a walking song are etched into a rock in Natural Bridge State Park.

This network of narrow, medieval passages has the most delightful name.

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

Corn-inthian columns with a uniquely American take on neoclassical architecture.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

Washington's iconic carousel has a nice piece of Civil Rights history.