Diego Rivera's massive tiled fountain and failed infrastructure project.

The spectacular subterranean collection includes dazzling minerals, including a piece of "kryptonite."

A 16th-century monastery boasts a lush array of plants native to Mexico’s most biodiverse region.

A tribute to one granddaughter's old apartment which now represents the whims of each visitor.

When you visit his grave, be sure to rub the Great Emancipator's nose for good luck.

This monolithic statue was erected in honor of Chief Black Hawk (even if it wasn't made to look like him).

It houses the remains of a 17th-century version of the Titanic.

One of the oldest living oak trees in the Southeast.

Oldest unrestored plantation house in America that is open to the public.

The world's longest known cave system.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

Home to the world's largest refracting telescope and the birthplace of modern astrophysics.

Former hotel turned into haunted playground.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

World's second largest particle accelerator, where nature reveals its secrets.

These pretty kitties killed and ate as many as 135 railway workers.