A walk through the historic city center, under the streets of Seattle.

The fifth-longest natural arch in the world, and the longest outside China.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

This historic hotel on Bathhouse Row in Hot Springs National Park has a storied history of gangsters and baseball greats.

This beautiful grotto is one of those places where you can't believe you're just outside Austin.

An enormous pink granite batholith, long attributed with spiritual powers by the Tonkawa Indians.

A recreated Stonehenge stands in a country field, complete with Easter Island moai heads standing as sentries.

A spring-fed pool so deep it's used for scuba diving as well as swimming.

Continuing the tradition of the dime museum in style.

Mysterious glowing orbs float through the desert night.

A popular swimming hole that hides one of America's most deadly diving spots.

Locals dubbed it the "Owl Building" because of its bird-like appearance.

A high-octane shrine to the greatest Texans who ever lived.

A small island hides in plain sight on Austin's Lady Bird Lake.

Life's work of sculptor Elisabet Ney remains preserved in her last studio.

Turning night into day in Victorian-era Austin to thwart a serial killer.

A former electrical substation is now home to an eccentric junk art masterpiece.

Free public park and gardens filled with peacocks and peahens.

A store full of vintage and indie toys designed to bring out the kid in even the crustiest of adults.

Austin’s nonprofit-run graffiti park where street art is meant to be painted over.

Home to the largest urban bat colony in North America, estimated at 1.5 million bats.

This unique structure in suburban Austin is made up entirely of other people's castaways, and constantly changing.