Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

Elevated freight railway turned wildly successful urban park.

A 400-foot-tall tall map of Chicago makes this once-ignored building stand out.

The unluckiest U-boat in the entire German fleet is now on display in a Chicago museum.

This abandoned ironworks was once the most important military supplier in America.

The body of St. John Neumann and his collection of hundreds of relics, on display in a Philly church.

The sounds of the world's largest fully functioning pipe organ dazzle shoppers at a Philadelphia Macy's.

A daily replay of the experiment that proved the rotation of the Earth.

Erected in 1697 this Philadelphia bridge is the oldest surviving roadway bridge and perhaps the oldest stone bridge in the United States.

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.

Yo, Adrian!

The first American department store, and home to the largest operating musical instrument in the world.

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

A mysterious shape catches the eye in this 16th-century painting.

The pockmarks across the building's facade are remnants of the Blitz.

The bronze uniforms commemorate the vital role of women during World War II.

This innovative steam machine was no doubt the most famous of the pioneer locomotives.

These mysterious Viking chess pieces spent centuries hidden on a remote Scottish island.

This marine reptile was discovered by one of the 19th century's greatest fossil hunters.

This unique bridge curls up like a caterpillar to let boats pass and then unfurls again to span a small canal.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

After nearly 60 years, there's still a bear at Paddington Station looking for help.

Thanks to modern navigational tools we now know that the true prime meridian runs through a park next door.