This abandoned prison castle has become an imposing gallery of graffiti art.

A wonderland of caves in eastern Iowa.

A replica of the self-taught naturalist's iconic cabin stands inside a library near his hometown.

At a mile long, the Fort Madison Bridge is the largest double-decker swing-span bridge in the world.

An underground wonderland in Iowa.

How did the 110-ton limestone statue cross the road?

Hidden in the grounds of the Fort Dodge Museum is a "real" and terrifying petrified giant.

This tiny site in Iowa, part of a patchwork national wildlife refuge, is home to ancient flora and fauna.

The oldest university museum west of the Mississippi retains its 19th century feel.

Chilly air billows out from the entrance of an abandoned mine on a steep hillside, providing a refuge for Ice Age fauna and flora.

This remote island in Iowa was abandoned after being devastated by flood.

The remains of a bustling turn-of-the-century park built to showcase the wonders of electricity.

An eclectic assortment of medieval architecture in a small Iowa town.

For just a few bucks, this Iowa funicular will let you feel like an 1800s fat cat.

The world's only three-story rotary jail is now a museum to a bizarre trend in prison design.

A warning to the weak-kneed: This narrow bridge does its swinging eight stories high.

This seemingly charming home memorializes and honors the victims of a century-old unsolved murder.

A half-mile long and three stories high, this bridge over the Des Moines River Valley mimics a descent into a mine shaft.

Nicknamed the "Grand Canyon of the North," this open-pit mine in Minnesota has a much shorter history.

Opened in 1956, the first modern indoor shopping mall in the world was inspired by the shopping arcades found in European cities.

Each of these 87 large stones has a unique message. Together, they form part of the Minnesota Military Family Tribute.

A hidden oasis in the heart of Minneapolis is also an Important Bird Area.

Terraced flowerbeds and rock sculptures in the midst of the Minnesota wilderness.

Direct, creative challenge to Mother Nature's winter wrath.