Featuring the last fully walkable parapet walkway in Europe.

One of the tallest bell towers in Italy plays a particular melody at just two times each day.

One of the best-preserved Roman amphitheaters is still used today, but for less brutal events.

One of the tallest lighthouses in the world also serves as a monument to the fallen of World War I.

A cone-shaped top and cylindrical body set this 900-year-old structure apart from other Italian bell towers.

This limestone outcropping was once a ceremonial site for ancient Native Americans.

A museum chronicling pioneer life constructed over Interstate 80.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.

Every drop of D.C. tap water flows through this old waterworks.

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

The "lovely red Vega" of the legendary record-settling pilot.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

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

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

This statue of the "father of television" stands prominently in the United States Capitol.

The walls of the iconic dome are hollow and have a secret stairway.

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.

The author's beautiful and historic home is also a fully functioning goat farm.

The mysterious 855-foot zigzagging stone wall has been baffling people for centuries.

View Kentucky's beauty and history from the perspective of painter John James Audubon, author and illustrator.

The flow from this waterfall sometimes comes out of springs below its rim.