The lynching and burial site of America's first train robbers.

A turn-of-the-century architectural marvel built on healing mineral springs and salt licks.

The world's largest collection of mechanical puzzles is a cornucopia of analog bafflers.

A lesser-known part of the Kinsey Institute is this impressive collection of art, artifacts, and material culture related to human sexuality.

The longest navigable underground river in the United States is home to countless blind and albino animals.

A medical facility that has been kept frozen in time.

The largest historic preservation organization in the United States.

This hidden stream beneath Indianapolis makes an appearance in the best-selling novel "Underground Airlines."

Ornate limestone building now filled with geologic specimens, and more.