This dramatic rail curve was once the target of a failed Nazi attack.

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

Steepest flood safety railway in the entire world.

This stone tower marks a lookout point over the historic Washington Crossing, and maybe some buried treasure.

A clone-tree in Washington Square Park sprung from seeds that went to the Moon and back.

The remains of a community that was forced to move for a dam that never materialized still rot in this Pennsylvania park.

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

Mysterious rocks that ring musically when struck.

Board a mine car and descend the #190 slope 300 feet underground into the Clark Vein of coal.

In which a local geological marvel becomes a quaint roadside attraction.

An indoor miniature village and labor of love for Laurence Geiringer, a model railroad enthusiast.

A toxic ghost town sitting atop a massive coal fire.

Once the world's largest reinforced concrete structure, this abandoned bridge now beckons urban explorers.

Rising out of a clearing in New Jersey's Pine Barrens is an Aztec-inspired monument to the "Lindbergh of Mexico."

A giant light 13 feet high shines near Thomas Edison's old Menlo Park lab.

How this Pine Barrens hill got its name is uncertain, but on a good day the view from the fire tower is crystal clear.

The highest point in New Jersey is marked by a massive, if simply named, obelisk.

These unassuming lighthouses have seen the first reading of the Pledge of Allegiance, the first wireless transmission, and more than one mystery.

This quaint New Jersey graveyard is an eternal resting place for thousands of beloved pets.

World Trade Center memorial likened to a woman's sexual organ.

Rusting away on the edge of New Jersey are the remains of a Cold War missile launch site.

Historic town settled in the 19th century because of its convenient location along a popular coal transport route.

Local lore claims this park is named after a young woman who jumped off a cliff.

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