The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

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

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

The world's longest known cave system.

The most loyal of little dogs, or a Victorian era publicity stunt?

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

A beautiful geyser under environmental threat.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.

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

A monument celebrating the idea of reaching inaccessible places.

Go inside to really appreciate this 500-year-old technological masterpiece.

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

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

The celebrated eyesore created by starry-eyed sweethearts.

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

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