On the wall of this medieval square, a symbol of the Spanish Inquisition.

This fountain was designed to honor the man who helped bring water to Barcelona.

Possibly the oldest church in Barcelona, this basilica has its pagan and Christian mythologies all mixed up.

The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

Named after a lodging site that existed nearby, a bridge has existed at this location since 1455.

Local legend says Isaac Newton built this footbridge without any screws, bolts, or nails.

Numberless clock creates a meal of time for the dreaded, insectile Chronophage.

Public opinion is still divided on this enormous sculpture in front of Baltimore's Penn Station.

This historic fort spans more the 300 years.

The privately owned cemetery that holds room for Washington's finest when they step down from life.

Parking garage where Bob Woodward met Watergate source "Deep Throat."

The National Park Service’s best-kept secret with views that rival any in D.C.

The story behind this beloved toy—named for Theodore Roosevelt and owned by his grandson—is more complicated than you might guess.

This Masonic lodge was the first major private building to be constructed in Washington, D.C. after the Civil War.

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

Yo, Adrian!

An abandoned cemetery lies in ruins as the surrounding forest swallows it whole.

World's first "penitentiary," meant to be humane, drove men insane.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

This former train station was once an important shipping depot for the regions farmers.

This groundbreaking 16th-century map is known as "America's birth certificate."