Oldest existing church in New York and the inspiration for Washington Irving's "The Legend of Sleepy Hollow."

This tiny church near Sleepy Hollow contains Henri Matisse's last work, a rose window, and nine windows by Marc Chagall.

The mosaic Star of David at the front of this store hints that it's no ordinary Italian grocer.

Seriously good slices of Sicilian pizza lurk at the back of the Bronx's oldest enclosed market.

Hidden inside one of the world's most well-visited zoos is a secret plaque promising eternal life.

Manhattan and the Bronx have been playing tug-of-war over this former island neighborhood for more than a century.

This old estate is a remnant of when the Bronx was a popular summer destination for wealthy New Yorkers.

Self-sufficient greenhouse floating on the Hudson River.

America's greatest forgotten garden and the former stomping grounds of Son of Sam.

An abandoned horticulture institute gloomily presides over rows of derelict and vine-wrought greenhouses.

The "Skinny House" is made from scrap, salvage, and a neighbor’s kindness.

A fake Transylvanian castle houses a cathedral of antlers.

A Hungarian pharmacy museum with a box full of mummy powder.

A museum in the childhood house of a medical pioneer.

Museum dedicated to the terror regimes of Hungary.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

A 19th century artistocrat's mansion, turned into a library, hidden in a modern library.

Amsterdam's former hotspot for public executions and dissections.

Three connected pink triangles memorialize persecuted gays and lesbians throughout history.

This unattributed sculpture in Amsterdam is hiding in plain sight.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

This impressive collection of rare books on ancient mysticism inspired author Dan Brown.

Established in 1638 to battle the Black Death, Hortus Botanicus Amsterdam is a treasure trove of rare flora.