This plaque commemorates the call between Alexander Graham Bell and Thomas A. Watson.

This bridge was the birthplace of a unit of measurement based on a fraternity joke.

The headquarters of one of the world’s longest-running humor magazines bears a noticeable resemblance to a head wearing a Prussian helmet.

This hidden labyrinth offers walkers some brief peace of mind.

An alley way dedicated to graffiti and street art is a constantly changing street gallery.

Dedicated to nine marines from Massachusetts who perished during the Beirut bombings.

This steep slide at a kids’ playground went viral after an police officer tumbled down it.

The colonial home of Paul Revere during the American Revolution.

Dedicated to a colonial woman who was hanged for being a Quaker.

In 1958, an MIT fraternity pledge laid down on this bridge and instituted a new, unique unit of measurement.

An interesting decoration on this historic site, this weathervane comes with as many legends as it does questions.

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

An easy-to-miss garden in Boston's North End honors the mother of JFK and others who lost children in WWII.

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

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.

One of the now-less-hidden floral gems of the "Emerald Necklace."

Over 100 million years ago, beach-bound dinosaurs left permanent marks on San Antonio's landscape.

This monument is dedicated to Balto, the heroic Alaskan sled dog.

Fake subway tiles were installed to cover a design that resembled the Confederate flag—it's unclear if the resemblance was intentional.

The only surviving sidewalk clock in Brooklyn.

An aptly-named street near the birthplace of the modern LGBT rights movement.

This neo-Gothic former auto showroom is one of the few remaining reminders of Brooklyn's "Automobile Row."

Hidden behind a gate in Greenwich Village is a little farmhouse that once served as the writing studio of a bestselling author.