The smaller of the three towers of San Marino is a former prison inaccessible from the ground level.

Standing atop 2nd-century Roman ruins, this church is one of the oldest and most iconic in Old Cairo.

An ancient instrument used to measure the waters of the Nile so Egyptian farmers would know whether to expect famine or flood.

Baroque celebration of the end of the Great Plague of Vienna.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.

The topiary maze at the Habsburg hunting lodge.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

A triumphant marble and bronze fountain depicting a 15th-century Hungarian king and his hunting party.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

Crafted from ocean litter, this sculpture highlights the ills of overconsumption.

A shrine-like museum entirely dedicated to soccer superstar Cristiano Ronaldo.

Portugal’s highest lighthouse has one of the most impressive focal planes in the world.

A lush oasis full of vibrant plants and striking geometric displays.

This glass skywalk offers vertiginous views down the volcanic cliffs to the beach below.

These small, triangular, colorful houses are a staple of Madeira Island.

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

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

A line of blue paint marks the route of the inaugural parade.

D.C. once had its own tiny rival to the New York Stock Exchange.

Before Nixon, "watergate" meant canals.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

An overlooked memorial honoring the local Washington residents who died in World War I.