Go inside to really appreciate this 500-year-old technological masterpiece.

Featuring the last fully walkable parapet walkway in Europe.

The remains of 50,000 World War I soldiers rest under a towering arch overlooking the Alpine battlefields.

Machismo turned on its head: the lady's hand goes to the dude with the bigger brain.

This medieval castle was home to a known tyrant and features several hidden passages.

Destroyed numerous times, this centuries-old bridge has always been rebuilt with its original design.

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

Turtles swim in a pond surrounding a classical temple in this lush park in Vicenza.

An intricately designed junk art house with four extravagant junk art cars hidden in the suburbs.

An ode to Japanese artist Hokusai, with a bit of a comical twist.

A single light illuminates one man's overshadowed contributions to street lamp history.

Designed to not only to represent the history of the local community but also, the future.

A lone tower rises above the cliffs in a city park, offering fantastic views of the Connecticut landscape.

The graffitied ruins stand hidden within the Pennsylvania woods.

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

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

Look closely and you’ll notice that the color changes a third of the way up the tower.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

Just outside the Naval Academy, Hell Point is a historical marker that could easily be the point where failed students wait for the bus.

This statue honors the author's groundbreaking family story.

The hidden ruins of a mill that is linked to an attempt to assassinate the vice president of the United States.

This abandoned Victorian-style house was built in 1884.