In the middle of a busy airport, a statue honoring the astronaut who told Houston that Apollo 13 had a problem.

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

A dedication plaque on this Boston tunnel is a microcosm of a massive, controversy-laden construction project.

The former home of a Boston physician whose murder led to a revolution in forensic science.

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

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

A stone marker commemorating the first time sound was transmitted over wires.

Created by a local artist, these quirky sculptures each have their own names and personalities.

A luxury hotel constructed out of a former jail.

What was once a true peninsula has now been filled in, causing the water to recede and leaving many streetside "waterfronts" and landlocked "islands."

A tiny plaque marks the location of the water source that facilitated the birth of modern-day Boston.

Stolen goods adorn the organ at Old North Church.

Dedicated to one of the darkest moments in Irish history.

This area was once known for being a lawless haven for rough-and-tumble sailors, earning the maritime-themed nickname "the black sea."

Historic Hull Street was actually the first street with a proper name in the Boston area.

This parking garage was the site of what was - at the time - the largest cash robbery in history.

A mysterious stone embedded at the base of a historic Boston building.

This historic patch of real estate offers a glimpse of colonial Boston.

This massive tea kettle was once a promotional stunt for the Oriental Teashop.

A more than 260-year-old crypt built on Boston's oldest English burial ground.

Narrowest house in Boston.

America's original house of worship for Spiritualism, the religious movement based on communing with the dead.

The history of the tea trade is told in bas-relief on this historic pair of Boston doors.

This bronze sculpture was inspired by a photograph of Martin Luther King Jr. and his wife embracing after he won the Nobel Peace Prize.