A park and memorial dedicated to the victims of the deadliest school massacre in American history.

This impressively complicated radioastronomy research center was once a tool of Soviet spies.

The center of the only hemisphere that awards visitors with a commemorative coin.

A science teacher's dream.

World's largest Christmas store.

Strange physical sensations and optical contradictions keep visitors coming back for more.

The fifth-longest suspension bridge the world, connecting one Michigan peninsula to another.

Former self-sufficient mental institution now a planned community.

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

Largest Roman Catholic church in North America.

A collection of unique outdoor sculptures surounded by the beauty of nature.

Penn State's giant bug collection.

The spectacular collection of one of the world's best woodcarvers.

The largest burial mound in the United States holds the remains of prehistoric West Virginians.

Little island known for its massive beachfront "flowerpot" pillars.

Lake within a lake.

Watch the newest land on the planet form before your eyes.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

Copenhagen's celebrated theme park and gardens.

Famously misunderstood wonder of the ancient world

Center filled with hands-on displays served as a tribute to several astronauts with connections to the state.

Largest tulip festival in America, includes fireworks, a parade, and a carnival.

Where most of the world's flypaper was made.

One man's attempt to create an artistic wonder on a run-down block in Detroit.