Hidden in Central Park's Ramble is a troublesome cave buried just beneath the surface.

A dilapidated dock tells the story of Titanic's missed arrival.

A hip bar decorated with walls of golden skulls.

A Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

Elevated freight railway turned wildly successful urban park.

Dodge prohibitionists and slide through the telephone booth in Crif Dogs.

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

An unassuming stone building houses New York City's oldest seismic station almost 30 feet below the Bronx.

Legendary private island in the Bronx...devoid of rats.

This plot of old-growth forest is the largest surviving remnant of New York City's original woodland.

The first and only carousel with a lineup entirely of insects.

The end of the 4 Line is also the end of the line for 300,000 souls in one of NYC's most illustrious cemeteries.

Home to the infamous "Typhoid Mary" and the worst loss of life in New York's history prior to September 11, 2001.

The loneliest island in New York.

The former home of the reclusive "Weird Wendels" who dominated New York real estate a century before Donald Trump.

A Christian-themed amusement park and complex rocked by scandals.

Oldest unrestored plantation house in America that is open to the public.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

This grand gothic brewery has been pumping out suds for over a hundred years.