This beautiful building in the heart of Manhattan's Financial District was empty for decades.

Tucked in the back of this amazing antique store is an important piece of medical history.

A crumbling hospital from the 1850s on Roosevelt Island.

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

This local gem houses the largest collection of pre-Raphaelite paintings outside of the U.K.

Final resting place of two dozen New York City harbor ships.

Where the embers of the Big Bang were first detected.

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

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

Beautiful stained glass depictions of the history of human flight fill this surprising chapel.

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

These lush botanical gardens employ the most purrfect pest control force.

This palatial botanical garden is home to one of the largest pipe organs ever installed in a private residence, and a piece of Wood's cycad.

Philadelphia boasts one of the best — and most often overlooked — traditional Japanese gardens in North America.

Mysterious rocks that ring musically when struck.

The origin of this mechanical boy was a mystery until he revealed his maker by writing it in perfect cursive.

A tour de force of a fountain, memorializing a man who loved fountains more than anything else.

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

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

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