Bizarre Cavern.

A star fort along the C&O Canal in western Maryland that protected America in three wars.

A pre-Industrial Age iron furnace and the site of a nearly-forgotten piece of Black history.

This extraordinary Depression-era expenditure was modeled after a postcard of a Mediterranean hotel.

What looks like a simple quaint estate in rural Pennsylvania was in the 18th century home to a small monastic community.

This might just be the TARDIS of bookstores.

This historic old movie house was the scene of one of the Blob's most iconic attacks.

This hidden gem of a garden has one of the only surviving Victorian ferneries in America.

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

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

This little-known collection holds everything from "Dracula" notes, to the manuscript of "Ulysses," to the forged works of Shakespeare.

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

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

A rare view of a preserved Victorian science museum.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

The middle finger of modernity.

A lover's walk between hilltop towns, decorated with graffiti love notes.

Five candy-colored villages on the Italian Riviera.

The bomb-ravaged remains of of a colossal Neptune.

The remains of an ancient Roman city are hidden underneath Bologna's beautiful public library.

Two stone columns flank the grand Venice square, but there were supposed to be three.

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

When a supermarket opened up shop within a medieval building it became protected by UNESCO on a technicality.

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