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

Ride the subways of yesteryear.

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

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

One of New York's best collections of pinball is hidden in a secret bar in the back of this laundromat.

Sniff the Titan Arum's rotting flesh.

The world's oldest hologram gallery and the labyrinthine laser laboratory of a holography pioneer.

A curious fountain that has no water and includes Satan, a crab, and 9 giraffes.

Feral cats keeping the rodent population at bay all across Greenpoint waterfront.

This striking arch, one of the first architectural elements constructed in Prospect Park, was recently restored to its original glory.

Sip a cappuccino in the historic cafe that introduced them to the United States.

This suburban enclave is home to a very unique art exhibit.

The institution is sitting on a goldmine of 21,000 paints, varnishes, pigments, and primers preserved for posterity.

Peruse rare tomes like poetry bound in pearls or books with branches and berries growing out of their spines.

Though strikingly beautiful, Seattle's other railway station is now largely forgotten.

Deep into the lower floors of Pike Place, find a date with fowl fate.

The United States Capitol's former columns still stand.

This intricately spiralling forest was created as a monumental work of art.

Menacing or in memoriam, the Silent People and their meaning are left to interpretation.

The tiny, studious rodents greet visitors to the National Archives of Finland.

The façade of this building looks like a bingo board, but it's really a giant clock by a famed graphic designer.

The best way to get a sneak peek at the movies.

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

Manhattan’s Battery Park has a whimsical carousel full of spinning, glowing fish.