The walls of the iconic dome are hollow and have a secret stairway.

The house where John Wilkes Booth conspired with his co-conspirators.

The United States Capitol's former columns still stand.

Macabre headstones carved with winged skulls, dancing skeletons, and pithy reminders of impending death.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

This sculpture by artist Fritz Keonig survived the 9/11 attacks and now stands as a monument to the victims.

A giant donut stands as a popular symbol of Los Angeles iconography.

This iconic L.A. bookshop is housed in an abandoned bank—both symbolic and chic.

This strange seaside tower got its name from a wealthy eccentric who would hide coins among its stones.

The oldest working bell set in North America, the bells at Old North Church sat silent for their first four years in Massachusetts.

Mrs. Mallard and her brood are a beloved fixture in Boston Public Garden.

A former waterfront market is now in the center of town due to some interesting Boston engineering.

This monument on Breed's Hill proves that one of the most famous battles of the Revolutionary War is misnamed.

The site of Paul Revere's historic two lantern warning.

The American Revolution was galvanized into serious action due to the tragic clash with British soldiers that occurred at this location.

Narrowest house in Boston.

A statue in Budapest's Liberty Square honors the former U.S. president's efforts to end the Cold War.

A random tree outside a Budapest hotel has become a DIY shrine to the late singer.

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

19th century pendulum and a clock restored by a rogue group of guerilla artists.

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.