A hidden network of subterranean passageways lies tangled beneath Indianapolis' bustling City Market.

This freshwater spring fills with 10,000 gallons of water per minute.

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

A layered tribute to the work of mosaicist Isaiah Zagar.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

Huge masonic hall in Philadelphia with lavishly themed rooms.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

The 340-year-old house that inspired the classic Nathaniel Hawthorne novel.

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

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

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

The first declared National Monument in the United States.

Home to the deepest rift anywhere on Earth.

This rugged area of red rocks and arches is often considered one of the most beautiful places on Earth.

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

20,000 pieces in a Frank Gehry-designed building.

Equal parts record-breaking temple to consumerism and bizarre fun park, it's more than you think it is...

A beloved Chicago music venue offering cold beer and lots of “Friendly."

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

World's largest Christmas store.

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

One of the largest crucifixes in the world stands 55 feet tall in a secluded, wooded area of northern Michigan.

There is an art, a science, and certainly a responsibility to occupying The Big Red Chair, and this is where it's learned.

Former self-sufficient mental institution now a planned community.