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

Huge masonic hall in Philadelphia with lavishly themed rooms.

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.

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

The highest point in Delaware is located under a trailer so this marker across the street will have to do.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

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

Instruments, apparatus, and rare books all relating to chemistry and its related sciences.

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

An unusual assortment of steerable wooden sleds is on display in a library in New Jersey where they were first invented.

A layered tribute to the work of mosaicist Isaiah Zagar.

This collection of odd proofs of concept is like taking a walk through the imagination of a Victorian engineer.

One of the oldest of its kind.

Ant sculptures march up the side of what used to be an iconic spot in punk rock lore.

A museum dedicated to the strange and extravagant costumes and memorabilia of the mummers, a tradition older than Philadelphia itself.

This splendid Versailles-inspired mansion has the largest French-style formal gardens in North America.

Current docking place of the SS United States, the fastest transatlantic ocean liner.

Enchanting gardens surround a derelict mansion, all hidden in plain sight behind a stone wall.

This weeping, 10-foot-tall sculpture was a maquette for a 9/11 memorial.

The tombstone of the founder of the lost town of Ogletown is now stuck inside a traffic median.

North America's oldest quarantine facility was built in response to Philadelphia's 1793 yellow fever outbreak.

This little-known Revolutionary War fort is supposedly haunted by the ghosts of its past.

A drab two-story office space in Delaware is a hidden tax haven for Hillary Clinton, Donald Trump, and over half the Fortune 500 companies.