Erosion and time have created a naturally-formed water park.

Giant granite rocks standing end-to-end like a train of circus elephants.

400 million-year old limestone caverns nestled in the Ozarks served as shelter and a hideout for cultures throughout North American history.

This titanic oil company sign is a reminder of the Americana boom of the 1970s and also its commoditization.

Less a museum than a bizarre fantasy world created by artists and engineers.

Where monkeys run wild and the humans are caged.

A mysterious castle built as a monument to lost love.

A monument celebrating the idea of reaching inaccessible places.

America's oldest archaeological site or a muddled case of wishful thinking.

The first American department store, and home to the largest operating musical instrument in the world.

A rare view of a preserved Victorian science museum.

World's first "penitentiary," meant to be humane, drove men insane.

A layered tribute to the work of mosaicist Isaiah Zagar.

Tour the dark and beloved poet's former cobwebbed basement, which may have inspired "The Black Cat."

Dr Barnes' $25 billion private collection of art and arboretum.

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

This little-known collection holds everything from "Dracula" notes, to the manuscript of "Ulysses," to the forged works of Shakespeare.

Two thousand artifacts from around the world collected by one woman who loved to travel.