Earth's tallest volcano is sacred to Native Hawaiians, and home to a dozen world-class observatories.

More than 2,000 species of tropical plants call this nature preserve and sanctuary home.

What was once a trend-setting, phrase-coining icon of architectural splendor is now a rotting, forgotten hulk.

A once grand hotel is being retaken by the wilderness it once capitalized on.

An abandoned castle owned and ignored by Masons carries a cursed history.

The abandoned ruins of America's first private zoo are open for exploration in the Catskills.

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

A mysterious air force base built to resemble a Long Island fishing village.

A former poultry store that looks like a giant duck and is one of the "seven wonders" of Long Island.

The oldest surviving bridge in New York City, which reopened to pedestrians in 2015.

Thriving meadows span a rooftop in one of Brooklyn's most heavily industrialized neighborhoods.

This Queens hospital has stood abandoned for almost 20 years after its patients were secretly relocated in the dead of night.