In the Shawnee National Forest, amazing rock formations peer through the treeline.

A geological oddity formed by two rivers carving out a mass of limestone on both sides.

The seventh largest spring in the world.

European castle ruins in an American state park are actually the product of death and grief.

The lowest point in the state of Illinois, at the confluence of the Mississippi and Ohio rivers.

An average of 33 million gallons of water pour out of the collapsed cave at the heart of this spherical spring.

Once an ambitious nature spa, these forest ruins now provide a serene monument to failure.

The deepest spring in Missouri.

Nestled in Onondaga State Park, over 100 canoes carefully stacked in a replica of the famous standing stones.

This former small town was destroyed not by the motor oil it sprayed the ground with but by the toxic waste that was added.

Quirky water tower advertises the long-gone Brooks Tomato Products Co.

During the 19th-century, this park was a vital trading fort.

A late sculptor's last project was to turn this abandoned cement factory into a castle-themed amusement park.

A floating museum that was sunk by a flood and left to rot in the tides.

An urban forest overtakes what was the greatest failure of utopic urban housing.

Giant works of art interspersed throughout meadows and woodlands offer a new discovery at every turn.

An abandoned meat mecca now serves as an excellent locale for urban exploration.