The vast, legendary catacombs hold secrets much stranger than stacked bones.

New York City's smallest piece of private property.

The site of the deadly Triangle Shirtwaist Factory Fire.

Touching mementoes from those who didn't make it back from World War I still hang in one of New York's oldest bars.

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

This sculpture by artist Fritz Keonig survived the 9/11 attacks and now stands as a monument to the victims.

Series of storm drains connected to a dark urban legend.

This jail which was in service for over a century is now open for curious visitors.

The site of one of history's most indelible and horrific tragedies.

Destructive children, start your engines.

An Irish Memorial commemorating those who perished due to potato blight.

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

Mural made of 100,000 pieces of hand blown glass, and until recently, the largest glass mural in the US.

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

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

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

A daily replay of the experiment that proved the rotation of the Earth.

The body of St. John Neumann and his collection of hundreds of relics, on display in a Philly church.

World's first "penitentiary," meant to be humane, drove men insane.

One artist's love letter to his city and its citizens plays out across dozens of bright murals painted on the sides of decrepit buildings.

The famous bell was secreted away and hidden in a church in Allentown during the British occupation of Philadelphia.

Mysterious rocks that ring musically when struck.