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

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

A terrific purveyor of natural history objects and curios.

Right angles in the forests of Panama.

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

A retired oil tanker now offering amazing views of New York City.

This secluded ruin was once a home for exotic plants.

Records of the dead describe the myriad odd ways people used to die.

This neighborhood grocery houses a treasure trove of Eastern European delights.

Walk into the 19th century without leaving Brooklyn.

Behind a bodega is a small museum of relics and ephemera showcasing the history of New York.

With its vast selection of books, comics, and records, this nearly 70-year-old open-air market always rewards the patient browser.

Honor one of Argentina's most prolific writers at his historic home.

The humble tomb of an Argentine general, hand-built by his son using stones brought down from the Andes.

A beautiful riverside mansion where the intellectual life of early-20th-century Argentina flourished.

The narrowest house in Buenos Aires is less than 10 feet wide.

A vast necropolis where you'll find the elaborate mausoleums of Argentinian tango stars.

A beautiful young girl said to have been buried alive in her coffin…

A tower devoted to — and modeled after — the Divine Comedy.

A gateway to a mysterious network of underground tunnels.

Museum housed in underground tunnels that date back to Buenos Aires's earliest settlements.

105-foot wide giant metallic flower blooms anew every day in the heart of Buenos Aires.