Millions of numbers carved in glass represent the tattoos forced upon victims.

Dedicated to one of the darkest moments in Irish history, this memorial has faced its fair share of backlash.

This headstone marks the grave of an 11-year-old boy killed during clashes in the streets over the boycotting of British goods.

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.

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

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

Golden and naked, the figure that was once the highest point in New York is all that remains of the second Madison Square Garden.

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

The ruins of this abandoned fort now stand as a picturesque reminder of America's march West.

This museum started as a collection of Manhattan Projects and continues to add exhibits as they are declassified.

A small metropolis of Pueblo cave dwellings have been carved right into the hillside of this national monument.

Despite time, colonization, and the brutal New Mexican heat, these Pueblo ruins still stand.

A museum dedicated to the alleged Roswell Incident.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

Elevated freight railway turned wildly successful urban park.

The world's longest known cave system.

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

Dedicated to the history of the 1,000 nuclear missiles that once covered the Great Plains.

One of America's first dinosaur parks gives a window into Depression-era paleontology.

This prehistoric sinkhole lured exclusively male mammoths to their death, much to the delight of science.

The granddaddy of all tourist traps, built on ice water, jackalopes, and a giant dinosaur.