Berthed at the Charlestown Navy Yard in Boston, "Old Ironsides" is the oldest commissioned warship still afloat.

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

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

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

One of the oldest used bookstores in the U.S. has been selling antiquarian treasures since 1825.

Two thousand artifacts from around the world collected by one woman who loved to travel.

A morbid secret lies hidden within the beautiful walls of the Boston Athenaeum.

An enormous, inside-out glass globe built in 1935.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

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

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

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

A museum of carnival attractions where you are invited to ride the rides.

Macabre astrological automaton clock dating to the late 1400s.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

A semi-scholarly approach to sex.

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

This massive library holds what was once the largest book collection in the world.

Elevated freight railway turned wildly successful urban park.

The only structure left with direct ties to the Salem witchcraft trials of 1692.

France's most famous cemetery, with some of its most curious tombs.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

The vast, legendary catacombs hold secrets much stranger than stacked bones.