One of the few remaining American elm trees in New York’s Tompkins Square Park was the birthplace of a new religion.

In its day this historic fort held 100 cannons pointed in almost every direction to protect New York.

The first piece of public art dedicated to LGBT rights.

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

A terrific purveyor of natural history objects and curios.

The artist and New York City icon lived, worked and died in this converted carriage house owned by another iconic artist, Andy Warhol.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

Paris' fabled purveyor of exotic taxidermy and natural history curios.

Natural history museum celebrating biodiversity with a parade of taxidermy animals.

The video game-themed street art first popped up in the French city.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

Sky ships, planes, and portraits left as unique tokens of hope and thankfulness.

This is the oldest Roman-made bridge in the city still existing in its original state.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

A massive marble foot is tucked away in a small alley near the Pantheon.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.