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

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

This small museum gives visitors a chance to soak up the history of the "sponge capital of the world."

No one knows how or why this painting appeared to produce crystallized tears.

On the upper deck of this church-owned parking garage stand eight pillars topped with different Catholic saints.

The so-called "Father of Las Vegas" had the city's first telephone installed in his office in 1907.

Now a pedestrian bridge, this was once part of a narrow-gauge railroad that ran along the east coast of Kauai.

Hawai'i's oldest wooden house was shipped around Cape Horn from Boston in 1820.

This monument built by Japanese American immigrants spent decades underground.

A glass display case holds the document that ended the Second World War—which one person signed on the wrong line.

A burial ground for workers at one of Hawai'i's largest sugarcane producers that laid buried for decades.

The only subway station in the city that still makes use of gap fillers.

Enjoy dishes that founding fathers once ate at this Colonial Williamsburg pub.

These markers are used to document elevation changes around the famed dam.

These markers are used to determine the ground stability of the Strip.

Ancient serpentine sacrifice holder that has stood the test of time.

Overlooking the Colorado Convention Center is this giant sculpture made from thousands of triangles.

Pillars made of 700 pieces of luggage climb to the ceiling of Sacramento Airport's baggage claim.

This vast masterpiece of Moroccan architecture spreads across 20 acres.

The oldest monument in Marrakesh and the city's only surviving example of Almoravid architecture.

Hiding in plane sight.

This small stone building, the final work of a renowned artist, offers a peaceful environment with radiant, colorful glass windows .

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

A unique set of caves that spits waves back out into the ocean.