A double agent hid information for the Soviet Union beneath this bridge for more than 20 years.

One of the oldest of its kind.

An Irish Memorial commemorating those who perished due to potato blight.

Golden and naked, the figure that was once the highest point in New York is all that remains of the second Madison Square Garden.

The fastest transatlantic ocean liner sat abandoned in a Philadelphia shipyard for decades.

This elaborate towering structure was once famed for its revolutionary height.

Ant sculptures march up the side of what used to be an iconic spot in punk rock lore.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

A cablecar-station-turned-revolving restaurant with 360-degree views of the Swiss skyline.

The nearly 120-year-old piece of pork wears a brass collar and was once a man's "pet ham."

For nearly a year, General Ulysses S. Grant was based here during the American Civil War.

A home built with marble tombstones from the graves of 2,200 Union soldiers buried in a Virginia cemetery.

This memorial to the victims of the Romanian Revolution of 1989 is often compared to a potato on a skewer.

Affectionately known as "Lord Bot," this historic statue has a cult social media following and rightly claims to be “the most metal inhabitant of the Wren Yard.”

America's first public mental health facility.

This striking observation tower shaped like a spinnaker sail is the newest icon in historic Portsmouth.

The skeletal white beams stand as a monument to religious dissent.

This museum devoted to the gothic author holds such interesting ephemera as his socks and walking stick.

The oldest housing complex in Riga is a mini timeline of architectural trends.

Over 100 towers were built in Bologna during the Middle Ages, but only 22 survive.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

The only tennis court that falls under the jurisdiction of the central bank.

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

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