A concrete block embedded with thousands of pulled teeth was created by a local dentist to memorialize his dog.

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

The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.

A stone arch leads to a cavernous 1930s spring house tucked away in the Pennsylvania woods.

Eccentric concrete mansion and museum designed and built by hand from the inside out.

Huge masonic hall in Philadelphia with lavishly themed rooms.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

Where America's first doomsday cult awaited the end of the world.

A rare view of a preserved Victorian science museum.

Hellam Township is reputed to feature seven remote gates, which when passed through in the right order, open an entrance to hell.

Mysterious rocks that ring musically when struck.

An abandoned cemetery lies in ruins as the surrounding forest swallows it whole.

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

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

Center filled with hands-on displays served as a tribute to several astronauts with connections to the state.

The museum moved on, but the diorama remain.

A series of 33 stone markers maps an ancient 55-mile transportation route.

Egyptian Revival obelisks still rise over the old mine shafts.

At HopCat, a marker honors fictional creatures with the ability to travel the missing dimensions of Kcymaerxthaere.

This observatory comes complete with three separate telescopes and a dedicated community of amateur and expert astronomers.

This historic Jewish cemetery sits right in the heart of a Detroit car factory.

The honor of highest point in Michigan was almost given to the wrong peak before this mountain won out by 11 inches.

These sprawling mines once served as a source of plaster and today serve as a storage facility.

A subterranean world of tunnels links several buildings of this rare 19th-century asylum.