The only geyser in the state of Pennsylvania is caused by pressure from an abandoned coal mine outside of the ghost town Centralia.

The American Home, Re-imagined.

The location where the famed author and abolitionist began his journey to freedom.

The longest-covered bridge in the state of Maryland.

Tucked behind New Jersey's abandoned Gingerbread Castle lie the eerie ruins of a once-flourishing paper mill.

Hundreds of glow-in-the-dark objects light up a museum in a historic zinc mine.

The remains of the furnace and iron works that produced the massive Hudson River Chain still stand in the woods of New York.

A mysterious collection of stones stand outside a small New England town.

A railroad tunnel that, upon its completion, was considered one of the engineering marvels of the modern world.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

Lines from a walking song are etched into a rock in Natural Bridge State Park.

The world's largest squirrel statue clutches a pecan bigger than your head.

The world's largest collection of mechanical puzzles is a cornucopia of analog bafflers.

Artist James Turrell's ode to dawn and dusk on the campus of Rice University.

One of Philadelphia's largest murals resides hidden under this bridge.

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

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

Mural made of 100,000 pieces of hand blown glass, and until recently, the largest glass mural in the US.

A layered tribute to the work of mosaicist Isaiah Zagar.

The last of Philadelphia's wood-paved streets is now a landmark of terrible engineering.

This elaborate towering structure was once famed for its revolutionary height.

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

The sounds of the world's largest fully functioning pipe organ dazzle shoppers at a Philadelphia Macy's.

An old trolley bridge was converted into a breathtaking garden bursting with colorful flowers.